3dx 0.03 (3)dx=2 0.006 1+x △v=0.01 △v=0.01 例20求函数y=5")的微分 解∵y'=5mmIn5ln(tanx 5n(tanx)In5 cot x. sec2x ∴小y=5mx)ln5 cot x sec2xh6 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