Exploding Dots! Global Math Week 2017!

Hi all,

Life is getting away from me with some tough personal stuff. So I haven’t been as active with the online math teacher community/twitter/blogging/etc. for a while, and I sadly probably I won’t be for a while.

That being said, I really wish I could participate in this initiative that Raj Shah (no relation!) shared with me a while ago. But because of life stuff I might not be able to. But one of the biggest things I want to do is bring joy into the math classroom as a core value, and this does that. And I love the idea of a collective joyful math moment for students and teachers all around the world! I’ve done a bit of exploration with this initiative — exploding dots — and I think it’s fabulous and full of wonderment. What it takes? At minimum, 15 minutes of classtime! I highly recommend you reading the guest post I asked Raj to write (below), and joining in this worldwide effort to celebrate the interestingness of mathematics!




The Global Math Project is an invitation to students, teachers, and communities everywhere to actively foster their sense of wonder and to enjoy truly uplifting mathematics. Math is a human endeavor: It’s about thinking creatively, exploring patterns, explaining structure, and solving real problems. The Global Math Project will share a unifying, joyful experience of mathematics with people all across the world.
Our aim is to thrill 1 million students, teachers, and adults with an engaging piece of mathematics and to initiate a fundamental paradigm shift in how the world perceives and enjoys mathematics during one special week each year. We are calling it Global Math Week.
This year, Global Math Week will be held from October 10–17. The focus of Global Math Week 2017 is the story of Exploding Dots™ which was developed by Global Math Project founding team member James Tanton, Ph.D.
Exploding Dots is an “astounding mathematical story that starts at the very beginning of mathematics — it assumes nothing — and swiftly takes you on a wondrous journey through grade school arithmetic, polynomial algebra, and infinite sums to unsolved problems baffling mathematicians to this day.”
The Exploding Dots story will work in any classroom, with a variety of learning styles. It’s an easy to understand mathematical model that brings context and understanding to a wide array of mathematical concepts from K-12 including:
  • place value
  • standard algorithms for addition, subtraction, multiplication, and long division
  • integers
  • algebra
  • polynomial division
  • infinite sums
  • and more!
Teachers routinely call Exploding Dots “mind-blowing”!
“I am still amazed by this. Exploding Dots has changed my fifth grade class forever!” – Jo Anna F.
“This makes me WANT to teach algebra!” – Kristin K.
“YES!” Hands up in the air in triumph! Decades of believing I couldn’t do math—poof! Exploded!”  – Jennifer P.
Join us for Global Math Week, October 10 – 17, 2017!
During Global Math Week, teachers and other math leaders are asked to commit to spending from 15-minutes to one class period on Exploding Dots and to share their students’ experience with the Global Math Project community through social media.
You can join the movement in four easy steps:
1) See Exploding Dots for yourself
Here’s a brief overview: https://youtu.be/KWJVAjONqJM
2) Register to Participate at globalmathproject.org
3) Conduct an introductory Exploding Dots experience with your students during Global Math Week
All videos, lesson guides, handouts are available for free at globalmathproject.org. Since everything is available online, inspired students (and teachers) can continue to explore on their own.
4) Share your experience on Twitter during Global Math Week using #gmw2017
That’s it!
The power of the global math education community is truly astounding. To date, over 4,000 teachers have registered to participate in Global Math Week (#gmw2017) and they have pledged to share Exploding Dots with over 560,000 kids from over 100 countries! We already over half-way to our goal
Help us reach and thrill a one million students!
The Global Math Project is a collaboration among math professionals from around the world. Spearheaded by popular speaker, author, and mathematician James Tanton, partner organizations include the American Institute of Mathematics, GDayMath.com, Math Plus Academy, and the National Museum of Mathematics.

Bragging about my school

This is a milestone for me. I have been at my school for ten years, and this is the start of my eleventh. It’s the only school I’ve worked at. That’s a testament to my school, but more specifically, to my colleagues.

Last year, my school’s awesome director of communications contacted the math department to let us know that the one issue of the magazine she publishes four times a year was going to focus on math. And she wasn’t kidding! The cover of the magazine had most of my multivariable calculus kids on it (thinking deeply at the math-art show I helped put on last year)!


One of my favorite things is that the feature article with an alliterative title, Making Math Meaningful, was simply the transcript of a roundtable discussion we had. A bunch of math teachers got in a room around a big table, and we were led by our director of communications who had done her research and come with some questions. There was a digital recorder in the center of the table. And through talking with carefully crafted prompts, we got to think deeply and collectively about our own practice. I can’t even tell you how interesting it was to listen to my colleagues during that facilitated conversation, and how proud I was to be in a school with such like-minded folks that I have the opportunity to learn from. (If you’re a department chair or academic dean, consider doing this!)

I wish I could just post a PDF of the article for you to read, but alas, the whole magazine is online but can’t be downloaded. Here are two quotations to whet your appetite:

quote 0

quote 1.PNG

So if you want to read about a department that is doing strong work moving towards inquiry-based learning, and read the words of real teachers having a real conversation playing off of each other, I highly recommend you:

  1. Go to this site
  2. Make the magazine full screen
  3. Read pages 18 to 29

That is all!

Marbleslides, Squigles, Portfolios, Previewing: My Third TMC Recap Post

Another blogpost about takeaways from TMC17 which I may be able to use in my classroom.

Marbleslides Challenges

I love Sean Sweeney. He’s everything good in the world, packaged in humanoid form! He’s so welcoming and kind to everyone… he wants everyone to feel part of things. At the Desmos Fellowship, he was the person I felt most safe saying “I have no idea what the hell I’m doing” and he would hunker down and help. I think many others felt the same. Okay, enough of the love fest. I am going to share his my favorite which I desperately want to use in my classroom. First, a little note. There is a difference between reading something on a blog and experiencing it. More and more, I’m recognizing that. I think if I read about this, I’d think “cool story, bro” and be like “okay, I could do this, but is it really worth it?” But experiencing it like we did during his short presentation, it’s like “I MUST DO!”

Sean has made a number of Desmos marbleslide challenges (if you don’t know about this, google it). Here’s a gif from his blog. The idea is that the marbles drop and you have to create stuff on Desmos to make the marbles hit the stars.


He shared one with us, and everyone in the giant room got obsessed with drawing functions that would let us “win.” For our challenge, people used ellipses, used lines, used piecewise functions, use quartics. It was inspired to see all the different approaches, and all the play that resulted.

What was lovely about Sean’s facilitation is that he paused us after a while (note: a teacher trick is to say “I’m going to pause your screens in 5… 4… 3… 2… 1…”). You knew from the cacophony of groans that we were in a good place. Then he shared out different approaches. The diversity of “answers” for the challenge was fascinating.

He made this a regular thing in his classes. I love his poster which shows the diversity of responses:

marble.PNGSo how can I use this? I’m not sure yet. I need a way to keep it light and fun, but also with all that my kids have on their plates and their lack of time, I don’t know if they would take the time to do it without some incentive. After teaching kids how to restrict the domain of a function/relation, and reminding them of all they have at their disposal that they’ve learned about (trig, circles, lines, parabolas, step functions, etc.), maybe I need to have a 10 to 15-minute in-class challenge (with kids working in pairs, so they are comfortable). And then do it again two weeks later, in class (but not in pairs). And then… announce that we are going to have regular marbleslides challenges. And the winner(s) will get the bonus question on the next assessment without having to do it. Or maybe buy some cheap plastic trophies which get displayed proudly in class? I want kids to work on the marbleslide challenges outside of class because part of this for me is that I want kids who might be slower at processing or coming up with ideas to have the time to execute their vision. I don’t want this to be a timed thing. Though maybe each time I introduce a new challenge, I give everyone 5 minutes in class to work on it.

What I have to make sure to do is share publicly the diversity of answers, like Sean did with his posters.

I also had an idea about how to score it. Something like 1 point for each star. But maybe if we’re learning about conics, or tangent, or something else, I’d give a bonus point for using those functions. And maybe an additional possible bonus point or two for any additional creativity (teacher’s choice)?

Sean’s posts are here and here.


David Butler also presented a my favorite on squigles. The poster and his blogpost are here.


I am not one for acronyms, really. They often are forced. But what I like is that these are used to teach student math helpers how to work with other students. From David’s post:

SQWIGLES is an acronym that we use to help our staff (and ourselves) when teaching in the MLC Drop-In Centre. It is a list of eight actions we can do to help make sure our interaction has a better outcome and make it more likely students will learn to be more independent.

It was originally Nicholas’ idea to have something like this. He wanted something to help the staff choose what to do in the moment, and also to help them reflect on their actions and choose ways to improve. We noticed that our staff (and ourselves) needed something focused on actions rather than philosophies, because then it could be used on the fly to choose what to do. Telling staff they need to be “encouraging” or “socratic” is not all that helpful when they don’t know how to put it into action. Yet this is what many documents giving advice to tutors do. So we decided to focus on the actions instead.

The reason I wanted to blog about this is because I think it might be helpful to share with the student tutors at my school. We have a peer tutoring program called TEACH (probably an acronym, since I always see it written in upper case… but for what, who knows!). And I haven’t inquired if and how students get trained. But I’d love to do a short 10 minute presentation on this, and maybe do a few scenarios where kids can practice tutoring while other kids watch (fishbowl?) and take notes on which of SQUIGLES happened. (Not all need to happen! Just look for them.)

I think I should also have this on my desk, since I work with students one-on-one a lot and having that reminder can’t hurt!


I went to Cal Armstrong’s session on documenting student learning. Over the years, I keep on getting inspired to have kids make portfolios that they turn in to show evidence of different traits. And this came up again in that session. James Cleveland has done it. Tina Cardone has done it. I want to do it. But aaaah! The time to make it into a reality! Argh! But I really would love to make explicit some values — maybe not standards of mathematical practice (… or maybe throw of a few of them in there…), but things like perseverance or active listening or seeing a problem in a different way or acting with courage or helping someone understand something by asking good questions or recognizing your own a misunderstanding or changing for the positive as a group member in somewayAnd have kids document these moments or interactions. And then at the end of a quarter, turn them in. (But have a check in halfway through the quarter!) It would mean that they are looking for these things, looking to do these things. And recognizing that I value these things. Maybe they have a choice of things they can include — not all of them? Maybe they can take videos or photographs or write paragraphs or draw a comic — it can open-ended how they demonstrated this quality or action.

There is something that I think happens in my school. Kids form facebook groups (or maybe on some other kind of social media) for their classes, and I suspect lots of backchannel communication about the class happens on this group. I suspect a lot of it is positive and uplifting and helpful. I would love to encourage kids to submit that sort of stuff in their portfolio also, if it demonstrates whatever qualities were asked for!

I don’t know if I’m going to do this this year. But maaaaaybe?

Preview, not Review: Student Intervention

Kat Glass gave a my favorite on intervention with students who were failing. Part of it was a powerful and important note about language and using code-words instead of saying what you mean. We don’t have many kids that fail classes in my school. But one thing that did strike home was that sometimes when working with kids who are struggling, we put all our emphasis on remediation and it’s like we’re always playing catch up. But sometimes we need to remember that with a struggling student, one tack that we can’t overlook is previewing upcoming material. It can help kids be more engaged and confident in class, and it sets a good tone moving forward.

I do this sometimes, but I need to remember to do this more frequently. Although I do lots of discovery based work, I don’t think that previewing some of it with a kid, and working through some of the discovery with them one-on-one, and then them seeing some of it happen again in class is a bad thing. I’ll just have to remind them that they need to be careful about not letting other kids have the same insights they had — and their role is to help without telling.


Play! Create! Adult!: My Second TMC17 Recap Post

Here are some more TMC17 notes!

Don’t play with your food, damnit! Play with your math!

I love the idea of having kids engaging in recreational math. I don’t have much time to encourage that in my curriculum — or at least the only way I’ve found for that to happen is with my explore math project [posts 1, 2, 3; website]. Some kids get some extra math problems to work on at math club (usually problems from math competitions or brilliant.org), and kids do math problems on our math team. But that isn’t the spirit of what I want to bring to my school. I want to get kids just fooling around with math for fun! Tinkering! Thinkering! Building! Collaborating! So that’s why I fell in love with Joey Kelly (@joeykelly89)’s my favorite presentation. Where he shared with us Play With Your Math.play

He and a friend created it. Right now it has 15 sheets of paper that can be printed out, each with a challenge. The name, inspired. Design wise, fantastic. But the problems are captivating, easy to dive into, and many have this open-endedness that can lead to obsession. When I was at the Desmos Fellowship a couple weeks ago, they had these for us to work on as a way to get to know each other. Each table had a different one and we were encouraged to play, and meet others who were playing, and then move to a different table and meet and play when we felt like it. The one I spent all my time on, trying to come up with a strategy? One that I know will get my kids in competitive mode? Poster 5:


I liked getting to know people and I liked these problems! At TMC we were given poster 14 and I became obsessed. And eventually, I solved it (and a second more complicated one). But it took A LONG TIME and I DIDN’T CARE. I refused to go play boardgames at gamenite until I had climbed this mountain!

I need to brainstorm if and how I am going to use these in my school. Some initial ideas:

1. Leave copies of these in the library for kids to use. Or put many copies of all of them on a bulletin board for kids to take, so when they’re board and standing there, they just grab one and start thinking.

2. Use these when I need to fill a long block (we have double periods one out of every five times we meet our kids) and I don’t have a good idea.

3. Plan an Upper School math night, where we gather at a space in the school, do math, order pizza. Like PCMI’s “pizza and math” (was that what it was called? we can do better!). These can be the amuse bouche or the main event!

Math Art!

Speaking of recreational math, at TMC17 there was so much math art. I just wanted to share some of it!

Captivating! I hope at some point to learn how to make crochet coral. It feels like once I get in the rhythm, it could be so soothing. Actually, I wonder if it would be fun to have a MAKER MATH club where we make math stuff together. And create our own math art gallery. Things like the things shown here, but also like these, and origami (demaine and lang), and a menger sponge made of business cards, and design and 3d print these optical illusions, and carefully color in pictures from Patterns of the Universe, and create our own mathart coloring pages. If you are reading this and have ideas of things that we could make, let me know in the comments! You probably can tell this is something I’m actually totally *feeling* (FYI, for me, the definitive math art page is @mathhombre’s page here.)

How To Adult: Let’s Buy A House

So @rawrdimus gave a my favorite on how to adult. He was teaching calculus and wanted to keep his seniors engaged. So he came up with this project that had kids pick a few houses and figure out what they’d need to buy it. He was the banker (a hilarious banker) and gave them two different mortgage options (a 15 year and a 30 year, with different interest rates) and they had to figure out their monthly payments.

I know come the spring, the kids in my calculus class will have their attention wane. So I think something like this could work (this investigation on wealth inequality worked a few years ago)! But right now it’s a little bit like trying to put a square peg into a round hole. I need it to have some more calculus before I do something like this though. Maybe we’ll spend some time talking about e or we’ll do something with summing (in)finite geometric series, and maybe seeing that as a riemann sum? I think it’s totally doable — I just need to think a bit more! But if you want to get a sense of why I’m trying to make this happen, just watch Jonathan’s presentation and you’ll totally get it. (Here’s his blogpost.)

You Guys, Funny Quotes, #YouMatter, Sitting Down: My first TMC17 recap post

ARGH! I have too much in my head and don’t even know where to start. I want to blog about all the large and small things I want to take away with me from TMC17, but they are so disorganized in my brain. So I’m just going to do a Faulknerian stream-of-consciousness style post and get some of it out now.

Hey, You Guys! Words Matter

A while ago, I realized when I said “you guys” it was super gendered. So I just sort of said to myself I’ll say “y’all.” When I wrote emails to my classes, I pretty much say “Hi all!” And then… and then… someone brought up the “you guys” issue at a faculty meeting at our school, and in my head I was like “I don’t do that!” But for some reason instead of that reminder doing good, and reinforcing what I was doing, I found it impossible to not say “you guys.” Like when someone points out you say “um” a lot, or say “like” a lot. You just, um, like, end up, like saying it, um, more.

Glenn Waddell spoke about “you guys” at TMC, and it resonated with a lot of people.

So I think I have a plan. Thanks to a huge discussion on twitter (sorry, don’t remember who to cite), here are my options:

all, y'all (2).jpg
The + others was cute… someone recalled they would say: “Humans… and others…” which made me laugh! I think I my lean towards nerds and my loyal subjects because I like whimsy. And as another teacher I love says about her classroom: “It’s a benevolent dictatorship.” @mathillustrated said it’s fun to mix them up. We’ll see what I’ll do!

A thought: I should post this in my classroom so I can refer to it! And tell students what I am trying to do. And have them catch me if I say “you guys” (which of course will make me say it more!). And have an ongoing tally of how many times I say it. And when they reach a certain amount, I’ll bring them some treat. I like the message it sends: I care about words because I care about you. For some of you, these words don’t matter. But I’m doing this for the others of you for whom these words do matter. Also: help me get better because I need to be, and I’m happy to be called out when I mess up.

Other ideas that came up:

@EmilySliman has renamed ‘homework’ as ‘home learning’ [I called it ‘home enjoyment’ because of another colleague, but they have since left me! So I am free to rename it as I please!]
@gwaddellnvhs has renamed ‘student’ (passive) to ‘learner’ (active) [“Learners learn, and students study. I don’t care how much you study. I care how much you learn.” paraphrased from here]
@chieffoulis has renamed ‘tests’ as ‘celebrations of knowledge’ (someone else uses ‘celebrations of learning)

Now do I think things like this will make a difference? Probably not. Calling something “home enjoyment” won’t make kids enjoy it. But it’s stupid and goofy and that’s worth something. And I don’t doubt that making an effort to change language might make a difference to some students. And it can prompt discussion where I get to talk about my values and philosophy around teaching. (“Why do you call tests ‘celebrations of knowledge,’ your majesty?”)  I try to live and act those values, but sometimes talking about them can help too.

Kids Say The Darndest Things: Another Classroom Culture Thing

I was having dinner at Maggianos with a TMC 1st timer, @pythagitup. Over dinner, he was telling me about a quote board he did where he put funny things kids said up on display. The beaming of his eyes as he recounted his classes and their quote boards made me know he had done something special. I begged him to write a blogpost about it, which he kindly did here. Here are his top 12 quotes:


I just got sad as I was writing this part of the post, because I remembered that I don’t have my own classroom. I usually am in two or three different classrooms and share the space with other teachers. So doing things like this are trickier. Sigh. It did remind me of one year in calculus. Years ago. 2012-2013. Back then, I was actually a funny-ish teacher. Like pretty goofy. And that particular calculus class was gads of fun. Good and strong personalities. I don’t know why but in recent years, I have lost that spontaneousness and goofiness that I used to have. I’m much more even keeled. I don’t know what happened. Does that just naturally happen when you grow older? I am up at the board a lot less now-a-days, so maybe that’s it… less class-teacher-class-teacher interaction? Whatever it is, I’ve changed. But back then, we had a goofy class. And all year, a student was secretly taking notes on funny things I said, or funny things kids in the class said. And she gave it to me at the end of the year. It was one of the most meaningful things a kid has done. You want to read some of it? Thought so. Wait, you said no? TOO BAD MY POST DEAL.


The post about it is here.

Promoting Kindness & Gratitude

I want to do this explicitly in my classroom. I tried a post-it wall of kindness/gratitude once, but that didn’t *really* take off in the way I wanted it to. I probably should have blogged about that to share a failed venture, and why it failed (namely: I saw it as a tack on unimportant thing, so I didn’t build time in class for kids to do it, and also kids have difficulty sharing kindness/gratitude so helping them see different things as kindness/gratitude would have helped too). [I see “nominations” as a way to do this too, and also related to the material! post 1, post 2]

But I saw something super nice. @calcdave was wearing a clothespin clipped to the collar of his shirt. I couldn’t read it but I asked about it. He then gave me a huge bear hug… which I thoroughly enjoyed because @calcdave is awesome and who doesn’t want a hug from him… and then looked at the pin. On the front, it said something like “hugs!” and on the back it said:


And then the person take the pin off and puts it on the other person (I think that’s important… they pin it on!). This then continues… from person to person to person. I love that @mrschz got it from me, and has now bought clothespins, painted them, and written on them. She’s all in!

I am not comfortable hugging my kids. I’m not that teacher very often (until they come back from college and visit). But I could see this going in different directions.

(a) Making 10 pins, each with one side blank, and the other side saying things like “high 5! #youmatter” or “two good things! #youmatter” or “fistbump! #youmatter” [and the person who inquires gets a high 5, 2 good things said about them, or a fistbump], and then the clothespin travels. I like the blank side because the clothespin then begs the question… and having different responses

(b) Making a bunch of pins and giving them all out to one class and explaining the purpose. I would have to do this with a class that is totally into stuff like this. I can imagine certain classes having a majority of kids who groan and then throw the clothespin away. So I’d have to choose wisely and come up with a good framing/rollout.

This idea originated with Pam Wilson, who is a true gem.

When this idea made its way on twitter, @stoodle pointed out that @_b_p has done something related in his classroom. And I remember reading this, being like OH MY GOD I NEED TO DO THIS and then promptly forgetting about it. The TOKEN OF APPRECIATION. I mean the name itself gets me giddy!


But I like this idea for a few reasons. First: it is done only once a week. It doesn’t take away from classtime. I can do it during my long blocks (once every seven class days). Kids have all week to think about who they are going to give it to. Kids also get to alter it, so at the end of the year, it is a recollection of good.

I know people are going to hate me for saying this, but this upcoming year, I have small classes. I’m at an independent school, so my classes tend to be small. But I think I remember my tentative rosters being even smaller than usual. I like to have larger classes because I like the chaos and interaction and cross pollination of ideas (though not the grading nor comment writing). But I wonder with small classes this year, will this work? I need to think more about this.

Crouching versus Sitting

This wasn’t at TMC but I saw it on twitter and wanted to affirm its truth for me.


I am fairly good about this. I have kids sit in groups of 3 but the tables can fit 4, so I tend to just hunker down with groups when talking with them. In most classes, I almost always drag a chair with me from one table to another which doesn’t have one. I agree there is a huge difference between crouching and sitting. There is value in crouching… it sends the message “I’m here to sort of briefly check on you and see what you’re doing but I’m likely going to move on… things are on you… so persevere.” I tend to sit when (a) I need to ask the group a set of questions to see their understanding, (b) a group seems to be getting stuck beyond productive frustration, (c) when a group is having a heated or interesting conversation and I want to listen in [I tell kids to ignore me and just continue, which I know they can’t really do but they do a pretty good job] or (d) when my feet are tired and I just feel like plopping down somewhere. Ha! Just kidding!


Problem Solving with Trig

So I’m at #TMC17 and Rachel Kernodle nerdsniped me. Or rather, I asked to be nerdsniped. Her session is at a time when there were a lot of other amazing sessions I wanted to go to, so I wanted to know if hers was one where I could hear about it and get the gist of things instead of attending. After some internal debate, she said that since it involved working on a problem, and then using that problem solving to frame the session, the answer was maaaaybe not. But then she thought: maybe I can try the problem on you and see how it goes. As long as you’re willing to put in the time to problem solve. Of course I said yes.

First, you can see her session description, which then framed how I approached the problem:

triangle 2.png

And then this is what she gave me (but it was hand drawn):


From the session description, I knew I had to find the ratio of the side lengths, so I could find exact trig values for angles other than 30, 60, 90, 45.

Rachel also gave me a “hint page” which she told me to look at when I was stuck (and to time how long it took me before I opened it). Let’s just say I’m extremely stubborn, and so as long as I think I have the capability to solve something and I am not completely stuck, I knew I wasn’t going to open it. Turns out my stubbornness paid off, and I ended up solving it.

In this post, I wanted to write a little bit about my experience with the problem. Because now when I look at that triangle, I have an duh, there’s an obvious approach to use here and everything I know points at that obvious approach. And the answer feels really obvious too. It is funny that I’m almost embarrassed to post this because there are going to be people who see it right away, and I worry (irrationally) (math pun) that they are going to judge me for not seeing it as quickly as they did. Even though I know being good at math has nothing to do with speed. And that it was important to go through the steps I did!

It took me over an hour to solve this problem. I had to do a lot of play and make a lot of random leaps before I stumbled across the “obvious approach.”  And I needed to do that in order for me to mine it for lots of things. It was true problem solving. And I know I really deeply understand this because at first the problem looked flummoxing and interesting, and now it looks obvious and somewhat trite. That’s my metric of how I know I deeply understand something. There are still certain things that I teach that I don’t deeply understand: like how the cross product of two 3D vectors yields a third vector perpendicular to the original two. I have done the math, but it’s non-obvious to me why the crazy way we compute cross products give us something perpendicular.(When I only understand something by doing brute algebra, I rarely feel like I get it.)

I’m going to try to outline the messiness that was my thought process in this triangle problem, to show/archive the messiness that is problem solving.

  1. The first thing I noticed was 36 and 36 sum to 72. So I was like: obviously put two of those figures together, and just play around. Something nice will happen. I remember when seeing the problem that approach felt immediate, obvious, and would lead to the solution. I was like yes! I have an inroad! This is going to rock, and I’m going to solve it quickly! And I’ll even impress Rachel!


    That appraoch didn’t work. Nothing popped out. I saw 54s and 18s and 144s pop out. But those weren’t angles that helped me. But I did then realize something nice… 36 is a tenth of 360! So I was going to use a circle somehow in this solution. Obviously!

  2. So I drew this:
    and I was like, I have something here! But after looking around, I was getting less. You can see I was trying to draw in some other lines lightly and play around — I thought maybe creating other triangles within these triangles would work. But nothing seemed to pop out. At one point, I thought I had possibly created an equilateral triangle in this (even though I saw one of the angles was 72! I was clearly desperate!). I started to get dejected at this point. I knew the circle had something to do with it…
  3. But seeing that 54s and 18s and 36s and 72s kept appearing, I thought maybe algebraically I should play around with the numbers (adding in 180 also, since I can draw a straight line wherever) to see if algebraically I could get a 30, 60, or 45. I tried adding and subtracting numbers from the set {18, 36, 54, 72, 180} looking for 30, 60, or 45. I figured if I could somehow do that, then I could find a diagram that would have angles I could get side relationships from. And then like a domino effect, I could get others. I don’t know. But after like 2 seconds, I got bored with this and didn’t see it as very efficient. My intuition was strongly saying I was going in the wrong direction. So I stopped:


  4. At this point, I was pretty dejected. I was slightly losing interest in the problem, thinking it was too hard for me. I tried to “force” a 60 degree angle in a diagram of that original blasted triangle. Hope! And then hope dashed!

  5. Damnit! I know the circle had something to do with it. It is just too nice to abandon the circle! Maybe…

    At first I drew all ten vertices for a 10-gon. I started connecting them in different ways. I thought I could exploit the chord-chord theorem in geometry, but that wasn’t good. I tried in that second diagram to extract part of the circle diagram and investigate it more. And the third was just more of the same. At one point, I was like e^{i\theta}=\cos\theta+i\sin\theta and was thinking I could somehow think of this as a problem on the complex plane, where each vertex was e^{ni\pi/5} and then look at the real parts for the x-coordinate and the imaginary parts for the y-coordinate. Clearly my mind was whirring, and I was going anywhere and everywhere. I actually thought maybe this complex plane thing seems ugly but it will be so elegant. But then I realized I didn’t know where to go if I labeled each of the points on the complex plane. Done and done and doneAt this point I put the problem away. Nothing was working.

  6. But after a minute, I couldn’t let it go! I wanted to solve it!!! So I went back. I thought I was getting too complicated, so I went simple.


    Nope. Didn’t help. But for some reason, this diagram and looking at the 72 reminded me of something I hadn’t thought of before. This is the leap that helped me get to the answer. And I can’t quite explain why this diagram sparked this leap. Which sucks because this is that moment that led to the rest of the problem for me! But I immediately remembered something about 72s and pentagons. And it hit me.

  7. So I drew what this connection was. My brain was whirring, and I was somewhere good…  

    I remembered the 72 degree angle appeared in a star. And this star was related to a pentagon. And that the pentagon had something about the golden ratio tied up in it. So I knew that maybe the golden ratio was involved in the answer. And where does the golden ratio appear? When there are similar triangles and proportions. I had my new approach and my inroad that I thought would work. Two triangles next to each other failed. Circles failed. But star/pentagon might work!

  8. So I looked at the original triangle and tried to figure out where I could find a similar triangle. And so I drew one line and created a similar triangle. I labeled the two legs as having length “1.”

    Initially, I was thinking I could do something with the law of sines. Because if you think about it, this is the ASS case — where you have that 36 degrees (circled), the side I labeled 1 (circled), and the other side I labeled y (circled). But you note that last side could be in two different places, which is why there are two ys circled. I still think there is something fun that I could do with this. But as I was doing this, I realized I was making things more complicated.

    I knew that the golden ratio came out of a proportion. So I abandoned the law of sines for the proportion. I simply set up a proportion with the two similar triangles. I first found “?” by doing 1/y=y/?. So ? was y^2This was exciting. I knew the golden ratio came out of solving a quadratic. Yeeeeee! At this point, my excitement was growing because I was fairly confident I was almost at the solution.

    Then I labeled the part of the leg that wasn’t ? as 1-y^2 (since the whole leg length was 1). Finally I looked at the third triangle in the diagram that wasn’t similar to the original triangle. It was isosceles and has legs of y and 1-y^2 so I set them equal and solved and not-quite-the-golden-ratio came out! (There was a mistake I made where I set y^2=1-y^2 and got y=\sqrt{2}/2. But I then found it and rewrote the equation y=1-y^2. This was the most depressing part of it. Because I couldn’t find my error because I was so tired. I went through my work multiple times and nothing. But taking some time away and then looking with fresh eyes, it was like: doh!)

    And so that was the end. I found if the original triangle had leg lengths of 1, the base was going to have a length of \sqrt{5}/2-1/2.

    I was so proud. I was on cloud nine. I was telling everyone! SO COOL!!! 

It probably took me in total 90 minutes or so from start to finish. So many false starts at the beginning, and one depressing transcription error that I couldn’t find.

The point of this post isn’t to teach someone the solution to the problem. I could have written something much easier. (See we can draw this auxiliary line to create similar triangles. We use proportions since we have similar triangles. Then exploit the new isosceles triangle by setting the leg lengths equal to each other.) But that’s whitewashing all that went into the problem. It’s like a math paper or a science paper. It is a distillation of so freaking much. It was to capture what it’s like to not know something, and how my brain worked in trying to get to figure something out. To show what’s behind a solution.



A curriculum is more than a set of papers

I wrote, with my friend Brendan, an advanced geometry curriculum. I was insanely proud of some of it. For those of you who know me, you know I love writing curriculum. It takes time, so much time, but it flexes the best part of my teacher brain. I’m forced to think backwards (“what am I trying to really do here? what matters?”) and requires creativity (“how can I get kids from point A to point B by having them do the heavy lifting, but in that sweet spot where I’m not necessary but their collaboration is? where that moment of invention and surprise is real?”). It is tough, and a lot of what I do isn’t great. But even my worst is better than any textbook I’ve seen.

Back to geometry. A few weeks ago, I met with one of the teachers at my school who is going to be teaching advanced geometry. I shared all my materials with her electronically, but I met to talk through things in more detail. But this meeting reminded me of something I’ve felt acutely for a few years: a curriculum is more than a set of papers.

As I wrote each piece of the geometry curriculum (or as I worked with my colleague as he took the lead), I had so much whirring around in my mind. I knew the intentionality of the questions and their ordering. I knew where kids would stumble. I knew where I asked questions that had no answers — on purpose — to get kids to think. I knew that I included a particular question in order to prompt a class discussion. I knew there were placed I needed kids to call me over to have a discussion with each group individually.  I knew I had included questions which were designed for me to verbally ask follow up questions. And of course I knew which things were hastily designed and didn’t work out so well when teaching.

But as I was attempting to go through my materials with her, it struck me pretty hard how hidden and implicit all those things were in that collection of papers that she had.

A real curriculum needs so much more, if someone else is going to successfully use it instead of me. When creating materials for other people in my department, who are teaching the same material, I started writing comments/notes in Word when I had a teacher move that I had in mind when crafting the problems:

teacher notesteacher notes2teacher notes3

It’s also a good reminder for me in the future. These notes help me and my colleagues remember what I was thinking of when writing my stuff. When I started doing this, I realized how a curriculum is a set of problems/activities with the intentionality behind the problems and teacher moves spelled out

In the past few years, I’ve had the fleeting and recurring thought: hey, I should organize all my geometry, precalculus, and calculus files neatly, and put them online in a systematic order for anyone to access. Maybe all of it will be useful to someone, maybe bits and pieces. I still sometimes think that. But what keeps me back from doing it is that gnawing feeling in the back of my mind: things need to be spelled out so someone else understands the flow and intention of each thing. And how to use it in the classroom. Where to stop. How to start. If there were any important “do nows” that weren’t captured in the sheets. Or knowing that someone was written as extra practice or to reinforce an idea that a class in a particular year wasn’t getting.

Over the past two years, it’s become harder and harder for me to open my feedly app and read blogposts. (I find most of my blogposts through twitter now.) It’s just been hard to find the time, and I get overloaded. And I haven’t had time to blog much either. And that sucks. But one thing I love about blog posts — that you can’t get on twitter/facebook/ed research — is that they often illuminate hidden ideas and bring to life something inert. Like when I read a blow-by-blow about an activity/problem set/ worksheet. Something that shows me the thinking that went into creating it, or better yet, how things unfolded in a classroom. What teacher moves happened? What were students thinking? [1]

If I wrote materials… and had a blogpost about how each day unfolded with those materials… that would be a curriculum at its best in my eyes. Because life is breathed into it. It becomes three dimensional. It involves people. The teacher. The students. And it makes explicit what is happening and why. [2]

Note: Funnily enough, Sadie posted a great piece on the idea of “curriculum” the day after I started writing this one! It is definitely worth a read.

[1] I like writing these kinds of posts — though they take a long time. Here’s a recent one: https://samjshah.com/2017/04/28/multiple-representations-for-trigonometric-equations/

[2] Obviously I won’t ever have the time to do this. But it’s nice to fantasize about. An extensive 180 curricular blog. Writing this post also reminds me that I need to get back to regularly reading blogposts.