can anyone help me on this?

Question

http://i181.photobucket.com/albums/x85/ctti_3/Untitled-58.jpg

Answer 1

If you call the int =G(x)-G(0) where G(x) is the antiderivative of the integrand
d(Int)/dx= G´(x) =F´(x)= 3e^-6cos^2x
and F´´(x)= 3*e^-6cos^2x( 12 cos x sin x)
At x= pi/6 = 9*sqrt(3)*e^-9/2