Use this resultf(x)= e^{-x}cosx with domain [0,3pi/2]

a) 'A' is the area between the x-axis, y-axis and f(x). 'B' is the area between the x-axis and f(x). Determine the ration of A to B (preferably in terms of 'e')

I was unable to do this question mainly because I couldn't find a way to integrate f(x), be it by u substitution or by parts. Any help would be greatly appreciated. Thanks in advance.