设l为平面曲线y=x2从点O(0,0)到点A(1,1)的有向弧,则平面第二型曲线积分∫lyey2dx+(xey2+2xy2ey2)dy=______.

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问题 设l为平面曲线y=x2从点O(0,0)到点A(1,1)的有向弧,则平面第二型曲线积分∫lyey2dx+(xey2+2xy2ey2)dy=______.

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答案e

解析 令P(x,y)=yey2,Q(x,y)=xey2+2xy2ey2,有

曲线积分与路径无关.
方法一  改取路径y=x.
lyey2dx+(xey2+2xy2ey2)dy=∫01(xex2+xex2+2x3ex2)dx
    =∫011(2xex2+2x3ex2)dx=(ex2+x2ex2-ex2)|01=e.
方法二  用原函数法.
    yey2x+(xey2+2xy2ey2)dy=ey2(ydx+xdy)+xydey2=d(xyey2).
    ∫lyey2dx+(xey2+2xy2ey2)dy=∫ld(xyey2)=xyey2|∫(0,0)(1,1)=e.
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