Question

求∫e^xsin²xdx 要过程

Answer 1

∫ e^xsin²x dx
=(1/2)∫ e^x(1-cos2x) dx
=(1/2)e^x - (1/2)∫ e^xcos2x dx (1)

下面计算：
∫ e^xcos2x dx
=∫ cos2x d(e^x)
分部积分
=e^xcos2x + 2∫ e^xsin2x dx
=e^xcos2x + 2∫ sin2x d(e^x)
再分部积分
=e^xcos2x + 2e^xsin2x - 4∫ e^xcos2x dx
将 -4∫ e^xcos2x dx 移项与左边合并后除以系数
得：∫ e^xcos2x dx = (1/5)e^xcos2x + (2/5)e^xsin2x + C
将上式代入（1）得

∫ e^xsin²x dx = (1/2)e^x - (1/10)e^xcos2x - (1/5)e^xsin2x + C