sin²x=(1/2)(1-cos2x)
∫
e^xsin²x
dx
=(1/2)∫
e^x(1-cos2x)
dx
=(1/2)∫
e^x
dx
-
(1/2)∫
e^xcos2x
dx
=(1/2)e^x
-
(1/2)∫
e^xcos2x
dx
下面单独计算
∫
e^xcos2x
dx
=∫
cos2x
de^x
分部积分
=e^xcos2x
+
2∫
e^xsin2xdx
=e^xcos2x
+
2∫
sin2xde^x
再分部
=e^xcos2x
+
2e^xsin2x
-
4∫
e^xcos2x
dx
将-4∫
e^xcos2x
dx移到左边与左边合并后除以系数
∫
e^xcos2x
dx
=(1/5)e^xcos2x
+
(2/5)e^xsin2x
+
c
代回到原积分得:
∫
e^xsin²x
dx
=(1/2)e^x
-
(1/2)∫
e^xcos2x
dx
=(1/2)e^x
-
(1/10)e^xcos2x
-
(1/5)e^xsin2x
+
c
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