(2)L:x=φ(y)c≤y≤d ∫f(x,y)=(m),y+()h.( 推广:T:x=φ(1),y=v(t),z=0(t).(a≤t≤B) f(x, y, z)ds =∫m ∫lq(t),v(t),o(t)lq'2(t)+y"(t)+o"(t)dt (a<B) 上一页下一页返回推广:  : x = (t), y =(t), z =(t). (  t   ) ( ) [ ( ), ( ), ( )] ( ) ( ) ( ) ( , , ) 2 2 2            =  +  +    f t t t t t t dt f x y z ds (2) L : x = ( y) c  y  d. ( , ) [ ( ), ] 1 ( ) . 2 f x y ds f y y y dy d L c =  +  (c  d )