We are doing integrals and I have the problem that is the integral from 0 to pi/2 2cos^5x(dx) n=4 therefore, dX=pi/8

We are asked for the midpoint values and I got

(pi/8) (2 cos^5(pi/16) + 2 cos^5(3 pi/16) +2 cos^5(5pi/6)+2 cos^5(7pi/16))

I tried putting this into the google calculator and it didn't give me an answer. I assume that the " ^5 " is giving it a problem but I'm not sure. Any tips?