设X=q(,2二阶可导, y=y(t) dy_y oo dy o' (ty(t)-"(ty'(t) dx (t) d p(t) .k=p(ty(t)-"(ty(r q"(t)+y2(t)2, ( ), ( ), 设 二阶可导    = = y t x t   . [ ( ) ( )] ( ) ( ) ( ) ( ) 2 3 2 2 t t t t t t k        +    −    = , ( ) ( ) t t dx dy      = . ( ) ( ) ( ) ( ) ( ) 2 3 2 t t t t t dx d y         −   =