[x*(1+cos2x)]/2=x/2+(xcos2x)/2;∫xcos2xdx=1/2∫xdsin2x=(1/2)xsin2x-(1/2)∫sin2xdx=(1/2)xsin2x+(1/4)∫dcos2x∫[x/2+(xcos2x)/2] dx=x^2/4+[(1/2)xsin2x+(1/4)cos2x]/2+c