原式=∫x(1+cos2x)/2 dx=1/2∫xdx+1/2∫xcos2x dx=x²/4+1/4∫xcos2x d2x=x²/4+1/4∫xdsin2x=x²/4+1/4xsin2x-1/4∫sin2xdx=x²/4+1/4xsin2x+1/8cos2x+C
