Math homework help

Demonstrate that integrate (cos^m(x) cos^n(x)) with upper limit is (pi/2), lower limit is 0 dx; = ((m/(m+n)) integrate (cos^m-1(x) cos(n-1)x with upper limit is (pi/2), lower limit is 0 dx. Hence, deduce that integrate (cos^m(x) cos(nx) dx = (pi/(2^(n+1)) with upper limit is (pi/2), lower limit is 0.