∫e的负x次方乘以sin2xdx的不定积分是什么,
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∫e的负x次方乘以sin2xdx的不定积分是什么,
![∫e的负x次方乘以sin2xdx的不定积分是什么,](/uploads/image/z/641779-43-9.jpg?t=%E2%88%ABe%E7%9A%84%E8%B4%9Fx%E6%AC%A1%E6%96%B9%E4%B9%98%E4%BB%A5sin2xdx%E7%9A%84%E4%B8%8D%E5%AE%9A%E7%A7%AF%E5%88%86%E6%98%AF%E4%BB%80%E4%B9%88%2C)
∫e^-x *sin2xdx
=-∫e^-x *sin2xd(-x)
=-∫sin2xde^-x
=-e^-xsin2x+∫e^-x*cos2x*2dx
=-e^-xsin2x-2∫e^-x*cos2xd(-x)
=-e^-xsin2x-2∫cos2xde^-x
=-e^-xsin2x-2e^-xcos2x+2∫e^-x*(-sin2x)*2dx
=-e^-xsin2x-2e^-xcos2x-4∫e^-x*sin2xdx
∴5∫e^-x *sin2xdx=-e^-xsin2x-2e^-xcos2x
∫e^-x *sin2xdx=-e^-x *(sin2x+2cos2x )/5
=-∫e^-x *sin2xd(-x)
=-∫sin2xde^-x
=-e^-xsin2x+∫e^-x*cos2x*2dx
=-e^-xsin2x-2∫e^-x*cos2xd(-x)
=-e^-xsin2x-2∫cos2xde^-x
=-e^-xsin2x-2e^-xcos2x+2∫e^-x*(-sin2x)*2dx
=-e^-xsin2x-2e^-xcos2x-4∫e^-x*sin2xdx
∴5∫e^-x *sin2xdx=-e^-xsin2x-2e^-xcos2x
∫e^-x *sin2xdx=-e^-x *(sin2x+2cos2x )/5