Question

问一道数学题……急!1设y＝e的负x次方cos（3x＋1）求导数y’2设隐函数y满足xy＋ln y＝1,求导数y’

Answer 1

1.y=e^(-x)cos(3x+1)

y'=e^(-x)*(-1)cos(3x+1)+e^(-x)*[-sin(3x+1)*3]

y'=-e^(-x)[cos(3x+1)+3sin(3x+1)]

2.xy+ln y=1

两边同时求导：

y+x*y'+(1/y)*y'=0

y'*(x+1/y)=-y

y'=-y^2/(xy+1)