特殊情形 1)L:y=y(x)x起点为a,终点为b 则Pdx+Q=「{Px,y(x)+Q|x,y(x)y(x)k (2)L:x=x(y)J起点为c,终点为d 则「PQ=「{Px(,yx(y)+x(y),yh x=o(t) (3)推广F:y=v(),点a终点B z=(t)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 + =  + , , . ( ) ( ) ( ) (3) :      推广 t起点 终点 z t y t x t      = = = 