At TMC13, I was in a group of people talking about precalculus. One of the exercises we did was make a list of some of the topics we found challenging to teach as teachers — and we broke out in groups to try to come up with ways to tackle those topics.
My group’s topic was inverse trig functions. (This was with April, Dan, Greg, and Andrew.)
Our initial task was to find the deep mathematical idea behind the topic… why we teach it, what we think we can get out of it conceptually… and what we sort-of converged on is that the topic really illuminates the idea of inverses and restricted domains. And that’s about it. And when push came to shove, we decided we didn’t find that restricted domain is something we really care about. We decided we didn’t really care about the inverse trig graphs, and the work we put into that side of things wasn’t really worth what we little we were able to squeeze out of it. It’s not that it is horrible, but we just didn’t couldn’t justify it.
So, honestly, we decided to just focus on inverses, and the idea of them as “backwards problems.”
Thus, we came up with two things:
1. A packet that has students secretly engage with inverse problem work before they even know what they’re doing. So the first packet is meant to be used before any unit circle trig is introduced. (A few of us, especially April, did something similar in her classes, and randomly, Greg Taylor did a my favorites on the same essential idea!)
In fact, if I were to use this in the classroom, I would not even mention the words “trigonometry.” I would focus on the idea of coordinate planes and circles, and simply leave it there.
2. A packet that students work on after they learn unit circle trig — and that more formally introduced the idea of the inverse trig functions. It tries to draw connections between the unit circle, the sine/cosine graphs, and their calculators.
There are concept-y questions for both packets. I’m including both packets below in one document. I’m posting one with a few teacher notes, and one with the teacher notes hidden. (The .docx is here if you want to edit!)
Packet with teacher notes
Packet without teacher notes
We did all this planning in pretty much an hour and a bit — from start to finish. And then I pulled together the ideas to make this document. I’m not sure I was able to capture everything we talked about, but I think I got most of the big things. Apologies to my collaborators if I totally botched the translation of our vision to reality!