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第1992题:the second kind of integrals




Evalute exsin(2x)dx\int \mathrm{e}^x \sin(2x) dx .



A. exsin(2x)+2excos(2x)5\dfrac{\mathrm{e}^x \sin(2x)+2\mathrm{e}^x \cos(2x)}{5} +C+C


B. exsin(2x)2excos(2x)5\dfrac{\mathrm{e}^x \sin(2x)-2\mathrm{e}^x \cos(2x)}{5} +C+C


C. exsin(2x)+2excos(2x)3-\dfrac{\mathrm{e}^x \sin(2x)+2\mathrm{e}^x \cos(2x)}{3} +C+C


D. excos(2x)2-\dfrac{\mathrm{e}^x \cos(2x)}{2} +C+C



Neither ex\mathrm{e}^x nor sin(2x)\sin(2x) will reduce to zero no matter how many times we differentiate them. So we must use Integration by Parts twice and solve for the integral algebraicly to find the answer.
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