Look at her, that actress, perfectly explaining that diagram chase. Draws the right arrows too. Points at all the right parts of the diagrams. Pronounces everything correctly. Correctly dismisses the snotty student's objections. And the other actor even calls it a diagram chase.
Was the screenwriter a grad school dropout or something?
Huh, the Salamander lemma:
"If you don’t like diagram chases, it’s likely that you still won’t like them once you know the Salamander lemma. The salamanders chase the diagrams for you, but you still have to chase the salamanders. I think the salamander proofs are easier to explain (once you know the Salamander lemma), and it’s easier to see where you use the hypotheses. "
The titular salamander of the lemma, front and centre. They even drew little feet on it.
"I'm impressed -- her gestures are pretty much what I'd expect from someone actually teaching this proof. Did they use a math double for this scene?"
I love this YouTube comment. I want to be a math stunt double in the movies too.
@JordiGH I did a bit of googling and stumbled upon a Rolling Stone article from 1980: https://www.rollingstone.com/movies/features/its-my-turn-19801127
There's a couple of lovely paragraphs about Jill Clayburgh's preparation for the teacher's role (and the student actually studied maths!), but the article doesn't explain where the screenwriter's admiration for mathematics comes from.