# How do you determine the derivative of #xcosx#?

##### 1 Answer

Dec 17, 2016

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!