y=y(x) 「f(x,y)ds ∫x,y(x)l1+y2(x)x a<r<h a p( ∫f(x,yd d ∫q(y),yl√1 c12 (y)dy C<K<d vc =r(O)cos 8 y=r(0)sin] L f(, y)ds a<6<B rP fIr(e)cos e,r(e)sin 012(0)+r2(0)de =0 =y(t) z=a(t) f(x, v, z)ds a<t<B ()y(,o(o)g2(o)+y2()+o2(nt K心( , ) [ , ( )] 1 ( ) 2 ( ) f x y ds f x x x dx b a a x b y x L  ===== +    =    ( , ) [ ( ), ] 1 ( ) 2 ( ) f x y ds f y y y dy d c c y d x y L  ===== +    =     [ ( )cos , ( )sin ] ( ) ( ) ( , ) 2 2 ( )sin ( )cos                 f r r r r d f x y ds y r x r L   +  =====   = = [ ( ), ( ), ( )] ( ) ( ) ( ) ( , , ) 2 2 2 ( ) ( ) ( ) f t t t t t t dt f x y z ds t z t y t x t L    +  +  =====       = = =             