→m=r"(n),im2+ma.lim 4x-0∠x Ax->0∠x4x>04x->0∠x u=g(x)可导→u=g(x)连续 Ax→)0→n→>0 →Iimo=lima=0 ∠x→0 ∠n→>0 dfig() Ay → lim ∫"(u)·g'(x) 4x->0 Ax d∫(g(x) =f(u).g(x) 2021/2202021/2/20 11 x u x u f u x y x x x x         0  0  0  0 lim ( ) lim lim lim → → → →  =   +  lim ( ) ( ) [ ( )] 0 f u g x x y dx df g x x  = =    →    lim lim 0 0 0  = = → →   x u ( ) ( ) [ ( ( )] f u g x dx d f g x  =    u = g(x)可导  u = g(x)连续 x → 0  u → 0