∫xsin²xdx=(1/2)∫x(1-cos2x)dx=(1/2)∫xdx-(1/2)∫ xcos2xdx=(1/4)x²-(1/4)∫ xd(sin2x)=(1/4)x²-(1/4)xsin2x+(1/4)∫ (sin2x)dx=(1/4)x²-(1/4)xsin2x-(1/8)cos2x+C
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