Proof of derivatives of Sine and Cosine functions


Time: 4:05

Why does angle theta approach angle x? The hypotenuse h approaching x is also not explained but one can imagine it geometrically. However, theta approaching x is a bit hard to visualize.

Also, feedback in general for course creators - at times the proof seems rushed and does not go into details of some steps, even though other steps are explained well.

I agree, this lecture could use some updates. I’ve submitted a request for that.

In general this course is very thin on mathematical rigor, it’s more of a “Math and Calculus Intuitions” treatment. I think the use of detailed proofs is out-of-scope for the intended audience.

Hi @Nandan1

It should be angle phi approaching angle x.

Consider it an exercise and try to work it out by considering the following isosceles triangle (red) and right triangle (green).


Good luck!