Question

find the n th derivative of y=sinx and hence find the 9th derivative of the function.

Answer 1

\[
\cos(x) = \sin(\pi/2-x)
\]

Answer 2

\[
\sin(\pi/2-x) = -\sin(x-\pi/2)
\]

Answer 3

It helps to move out the negative, because \(\frac{d}{dx} \pi/2-x = -1\) but \(\frac{d}{dx} x-\pi/2 = 1\)