Question

What is the derivative of `cos(pi x)`?

Answer 1

`(dy)/(dx)=-pisin(pix)`

Explanation:

We use chain rule here

As `y=cos(pix)`

`(dy)/(dx)=d/(d(pix))cos(pix)xxd/(dx)(pix)`

= `-sin(pix)xxpi`

= `-pisin(pix)`