∫ xcos2x dx
= (1/2)∫ xcos2x d2x
= (1/2)∫ x dsin2x
= (1/2)xsin2x - (1/2)∫ sin2x dx
= (1/2)xsin2x - (1/2)(1/2)(-cos2x) + C
= (1/2)xsin2x + (1/4)cos2x + C
原创 | 2022-09-22 11:37:35 |浏览:1.6万
∫ xcos2x dx
= (1/2)∫ xcos2x d2x
= (1/2)∫ x dsin2x
= (1/2)xsin2x - (1/2)∫ sin2x dx
= (1/2)xsin2x - (1/2)(1/2)(-cos2x) + C
= (1/2)xsin2x + (1/4)cos2x + C