∫x^3cos2x dx=(1/2)∫x^3dsin2x=(1/2)x^3sin2x - (3/2)∫x^2.sin2x dx= (1/2)x^3sin2x + (3/4)∫x^2.dcos2x= (1/2)x^3sin2x + (3/4)x^2cos2x - (3/2)∫xcos2xdx= (1/2)x^3sin2x + (3/4)x^2cos2x - (3/4)∫xdsin2x=(...