对数求导,
lny=arctan[(1-x)/(1+x)]
整体对x求导,得
y'/y=[(1-x)/(1+x)]'/{1+[(1-x)/(1+x)]^2}
=[-2/(1+x)^2]/[1+(1-x)^2/(1+x)^2]
=-2/[(1-x)^2+(1+x)^2]
=-1/(1+x^2)
所以y'=-e^{arctan[(1-x)/(1+x)]}/(1+x^2)
对数求导,
lny=arctan[(1-x)/(1+x)]
整体对x求导,得
y'/y=[(1-x)/(1+x)]'/{1+[(1-x)/(1+x)]^2}
=[-2/(1+x)^2]/[1+(1-x)^2/(1+x)^2]
=-2/[(1-x)^2+(1+x)^2]
=-1/(1+x^2)
所以y'=-e^{arctan[(1-x)/(1+x)]}/(1+x^2)