Dylimc为有限大小CAx->0 △xAyAVn-ln-= c lim (Ay)"-limlimAyAx△r->0Ar->0AxAr-00n>1n<1±8
0 lim x y c c → x = 为有限大小 ( ) ( ) ( ) 1 1 0 0 0 lim lim lim n n n x x x y y y c y x x − − → → → = = 0 1 1 n n =
瞬时速度举例：x(t) = at?a(t + △t) - at?x(t + △t)- x(t)v(t) = limlim△t△tAt-0At→0a(t? + 2t△t + △t?)a(2t△t + △t?-at22at标记limlim△t△tAt-→0210dx=xdt
瞬时速度举例: 标记: ( ) ( ) ( ) ( ) at t a t t t t a t t t t at t a t t at t x t t x t v t x t at t t t t 2 2 2 ( ) ( ) ( ) 2 0 2 2 2 0 2 2 0 0 2 lim lim lim lim = + = + + − = + − = + − = = → → → → x dt dx v(t) = =