You know you’re a bit rusty from the summer when a teacher asks you to — without using L’Hopital — to prove that:
And you are like, oh, that’s easy.
And then — after two false starts — it takes you 3 minutes to figure out.
Just remember: you are a calculus teacher.
I’m going to say it again: you are a calculus teacher.
Maybe if I say it enough times, it will be true.
The technique for this problem is to substitute . Then a short bit of manipulation later, you’re there.