Well,
Here is the solution :
when you arithematically solve it you get cos4x.
Now,
cos4x
=> (1+cos2x)2 / 4
=> (1 + cos22x + 2cos2x)
=> [1 + cos2x + (1+cos4x)/2 ] /4
now, you can well integrate cos2x and cos4x easily !!!!!
you will get your answer !!!!!!!
And yes, no need to rate five times, once would do !!!!!!!