设L是从点(0,0)到点(2,0)的有向弧段y=x(2-x),则 ∫L(yex-e-y+y)dx+(xe-y+ex)dy=_______。

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问题 设L是从点(0,0)到点(2,0)的有向弧段y=x(2-x),则
L(yex-e-y+y)dx+(xe-y+ex)dy=_______。

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答案[*]

解析 P(x,y)=yex-e-y+y,Q(x,y)=xe-y+ex

令L0:y=0(起点x=2,终点x=0),
则∫L(yex-e-y+y)dx+(xe-y+ex)dy=(∮L+L0-∫L0)(yex-e-y+y)dx+(xe-y+ex)dy,
而∮L+L0(yex-e-y+y)dx+(xe-y+ex)dy
==-∫02dx∫0x(2-x)dy=-∫02x(2-x)dx=
L0(yex-e-y+y)dx+(xe-y+ex)dy=∫20-dx=2,
于是∫L(yex-e-y+y)dx+(xe-y+ex)dy=
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