cos(xy^2)=x+2y求导 y=x^1/x求导
问题描述：
cos(xy^2)=x+2y求导 y=x^1/x求导
答
cos(xy^2) = x+2y
-sin(xy^2) .( y^2 + 2xy.y') = 1+ 2y'
[2+ 2xysin(xy^2)]y' = -(1 + y^2sin(xy^2) )
y' =-(1 + y^2sin(xy^2) )/[2+ 2xysin(xy^2)]
y =x^(1/x)
lny = (1/x) lnx
(1/y)y' = 1/x^2 - lnx/x^2
y' =[1/x^2 - lnx/x^2] .x^(1/x)