What is the integral of cos^6x? I tried half angle identities but it didn't really help...

dx cos^n x = (1/n)cos^(n-1) sin x +[(n-1)/n] dx cos^(n-2) x

so
get cos^4 from cos ^6
then cos^2 from cos^4
then
dx cos^2 x = (x/2) + (1/4)sin 2x