設(shè)F(x,y)= x2/3 + y2/3 -1
先對(duì)x求偏導(dǎo)數(shù) 再對(duì) y求偏導(dǎo)數(shù) 在（x0,y0)點(diǎn)處的偏導(dǎo)數(shù)
Fx(x,y)=(2/3)x0^(-1/3)
Fy(x,y)=(2/3)y0^(-1/3)
切線就是 (2/3)x0^(-1/3)(x-x0)+(2/3)y0^(-1/3)(y-y0)=0
x0^(-1/3)(x-x0)+y0^(-1/3)(y-y0)=0
第一象限 x0 ,y0>0
求xy軸的正半軸交點(diǎn) (0,x0^(2/3)y0^(1/3)+y0)
(y0^(2/3)x0^(1/3)+x0,0)
求距離 ={^2+^2}^(1/2)
x0,y0 還滿(mǎn)足方程x2/3 + y2/3 =1 x0^(2/3)+y0^(2/3)=1
距離 ={^2+^2}^(1/2)
={^2+^2}^(1/2)
={^2+^2}^(1/2)
={x0^(2/3)+y0^(2/3)}^(1/2)
=1