求函x(sinx)平方的定积分,下限为0上限为1

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求函x(sinx)平方的定积分,下限为0上限为1
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求函x(sinx)平方的定积分,下限为0上限为1
求函x(sinx)平方的定积分,下限为0上限为1

求函x(sinx)平方的定积分,下限为0上限为1
答:
因为∫xsin²x dx
=∫x(1-cos2x)/2 dx
=1/2∫x(1-cos2x) dx
=1/2∫x-xcos2x dx
=1/2(∫x dx - ∫xcos2x dx)
=x²/4-1/4xsin2x+1/4∫sin2x dx
=x²/4-1/4xsin2x-1/8cos2x + C
所以∫(0到1)xsin²x dx
=x²/4-1/4xsin2x-1/8cos2x |(0到1)
=1/4-sin2/4-cos2/8-(0-0-1/8)
=3/8-sin2/4-cos2/8

int((x*sin(x))^2,0,1)
ans =
1/6 - sin(2)/8 - cos(2)/4
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