Question

How do you determine the derivative of `xcosx`?

Answer 1

Find the first derivative and then differentiate again.

`dy/dx= 1(cosx) + x(-sinx)`

`dy/dx = cosx - xsinx`

Differentiate again.

`(d^2y)/(dx^2) = -sinx - (1(sinx) + x(cosx))`

`(d^2y)/(dx^2) = -sinx - sinx - xcosx`

`(d^2y)/(dx^2) = -2sinx - xcosx`

Hopefully this helps!