3对坐标的曲线积分的计算: (1)直接计算法:方法:一代二换三定限 fPdr+edy x=o(t) y=y(t tma-piplo y=y(x Pac+二「m (Pl,y(x)]+elx, y(xly(x)be 从 → b Px+Q小y J从c→de (PIo(y), ylo(y)+elp(y), ylldy K心3.对坐标的曲线积分的计算: (1) 直接计算法: 方法：一代二换三定限  { [ ( ), ( )] ( ) [ ( ), ( )] ( )} . ( ) ( ) P t t t Q t t t dt Pdx Qdy y t x t t L   =====  +  + = = →             从 { [ , ( )] [ , ( )] ( )} . ( ) Pdx Qdy P x x Q x x x dx b a y x x a b L  + ===== +  = →     从 { [ ( ), ] ( ) [ ( ), ]} . ( ) Pdx Qdy P y y y Q y y dy d c x y y c d L + =====   + = →     从