求不定积分∫xcos2xdx 求过程答案!谢谢!
问题描述:
求不定积分∫xcos2xdx 求过程答案!谢谢!
答
∫ 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