How do you differentiate y=3xcos2(x)?

1 Answer
Feb 1, 2018

3cosx[cosx2xsinx]

Explanation:

d[uv]= vdu+udv this is the product rule, where v and u are both functions of x.

Let u =3x and v=cos2x

so we have ......cos2x.[3]+3x[2sinxcosx]

=3cos2x-6xsinxcosx.....=3cosx[cosx2xsinx].

cos2x=[cosx]2 and so need to use the chain rule to differentiate this, =2cosx, times the derivative of cosx which is -sinx, soddxcos2x=2sinxcosx. hope this helped.