且「P(x,y)+Q(x,y rP(PIP(O), y(l()+glp(0),y(Oly(o)dt 特殊情形 (1)L:y=y(x)x起点为a,终点为b 则P+qy={Px,y(x)+Qx,y(xy(xhx (2)L:x=x(y)J起点为c,终点为d JIL, Pdx+ody=(PIx(), ylx ()+2(x(y), yl)dy 上一页下一页返回P t t t Q t t t dt P x y dx Q x y dy L { [ ( ), ( )] ( ) [ ( ), ( )] ( )} ( , ) ( , )         =  +  +  且 特殊情形 (1) L : y = y(x) x起点为a，终点为b. Pdx Qdy {P[x, y(x)] Q[x, y(x)]y (x)}dx. b L a 则 + = +  (2) L : x = x( y) y起点为c，终点为d. Pdx Qdy {P[x( y), y]x ( y) Q[x( y), y]}dy. d L c 则 + =  +