3dx 0.03 (3)dy 0.006 1+x △v=0.01 △=0.01 例20求函数y=5y的微分 解∵y'=5 In5[n(tanx) 5nx)n5·cotx.sec2x dy=5 n(tanx) In 5. cot x. sec2xdx6 2 2 2 0.01 0.01 3 (3) 1 x x x x dx dy x = =  =  = = + 例20.求函数 的微分. ln(tan ) 5 x y = 解 ln(tan ) ln(tan ) 2 5 ln5 [ln(tan )] 5 ln5 cot sec x x y x x x   =  =   0.03 0.006 5 = = ln(tan ) 2 5 ln5 cot sec x  =   dy x xdx