`intcos^4xdx`

Explanation

`intcos^4xdx=int((1+cos2x)/2)^2dx`
=`1/4 int(1+2cos2x+cos^2 2x)dx`
=`1/4 int(1+2cos2x+(1+cos4x)/2)dx`
=`1/4 int(3/2+2cos2x+1/2cos4x)dx`
=3x/8+1/4sin2x+1/32sin4x+C