Question

In session 7, how do we know that (cos delta x - 1) over (delta x) = 0? And the same for the next equation - (sin delta x) over (delta x) = 1? It would seem to me that both are equal to 0/0.

Answer 1

Here is the proof for
\[\frac{\sin x}{x} = 1\]
http://www.khanacademy.org/math/calculus/v/proof--lim--sin-x--x
The same is shown in the lecture videos.

Answer 2

oh - I see, the limit of sin x / x is shown in session 8. I watched the first video again and he does say "I claim", and then in then in the next session the proof is shown