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设y=∫(0,π)e^(-x)sin2xdx
=-∫(0,π)sin2xde^(-x)
=-e^(-x)sin2x|(0,π)+∫(0,π)e^(-x)dsin2x
=0+2∫(0,π)e^(-x)cos2xdx
=-2∫(0,π)cos2xde^(-x)
=-2cos2xe^(-x)|(0,π)+2∫(0,π)e^(-x)dcos2x
=2(1-e^(-π))-4∫(0,π)e^(-x)sin2xdx
=2(1-e^(-π))-4y
y=2(1-e^(-π))/5
=-∫(0,π)sin2xde^(-x)
=-e^(-x)sin2x|(0,π)+∫(0,π)e^(-x)dsin2x
=0+2∫(0,π)e^(-x)cos2xdx
=-2∫(0,π)cos2xde^(-x)
=-2cos2xe^(-x)|(0,π)+2∫(0,π)e^(-x)dcos2x
=2(1-e^(-π))-4∫(0,π)e^(-x)sin2xdx
=2(1-e^(-π))-4y
y=2(1-e^(-π))/5
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