∂z/∂x=[1/(1+(y/x)²)](-y/x²)
=-y/(x²+y²)
∂z/∂y
=[1/(1+(y/x)²)](1/x)
=x/(x²+y²)
常用导数公式:
1.y=c(c为常数) y'=0
2.y=x^n y'=nx^(n-1)
3.y=a^x y'=a^xlna,y=e^x y'=e^x
4.y=logax y'=logae/x,y=lnx y'=1/x
5.y=sinx y'=cosx
6.y=cosx y'=-sinx
7.y=tanx y'=1/cos^2x
8.y=cotx y'=-1/sin^2x
9.y=arcsinx y'=1/√1-x^2
10.y=arccosx y'=-1/√1-x^2
11.y=arctanx y'=1/1+x^2
12.y=arccotx y'=-1/1+x^2