implicite differenciation to find slope of curve at apoint

Hi,

I would like to do some thing like

x^2+y^2=1
d(x^2+y^2)/dx=d(1)/dx
d(x^2)/dx+d(y^2)/dx=0
2x+2y*dy/dx=0
dy/dx=-x/y

but

syms x y
f=x^2+y^2-1
diff(f,x,y)gives

2y

please help..

Thanks,

Sita

[Sung Won Kim]

It would be better, If you use this When you defining f f=x^2+y^2==1

and I recommend to use syms x y(x) when you defining syms.

last, it is also necessary that diff(f,x) is used to differenciate the f by x (You don't need 'y')

then I think it will give an ans.

good luck

Kim

Answer 1

[Mischa Kim]

Sita, how about

 syms x y(x) f(x,y)
 f  = x^2+y^2-1 == 0;
 df = diff(f,x)