Squeeze theorem

Part of the demonstration made by the Twelfth Doctor. (TV: The Pilot)

The Twelfth Doctor once used the squeeze theorem to prove that $\lim _{\theta \to 0}{\frac {sin\theta }{\theta }}=1$. During the demonstration, the Doctor used mathematical concepts such as sin, cos, tan, inequalities and limit. (TV: The Pilot)

Behind the scenes

Although the name "squeeze theorem" wasn't used, and the demonstration wasn't explained by the Doctor, it is a faily basic differential calculus theorem, and can be recognised by the viewers.