Can one use fsolve with symbolic value equations?

Hello everyone. I am wondering if in Matlab, one can use symbolic variables together with fsolve. I have to equate a gradient (calculated from substituted variables) to zero. Here is what I tried. Could anyone tell me what is wrong with this? If I can't use fsolve with symbolic value equations, how could I solve for 2 nonlinear symbolic valued equations with two unknowns? Tks:

function gradB = myfun(X)

syms X(1) X(2) n m

B = subs(X(1)+ X(2), [X(1), X(2)], [n+m, n-m]);

gradB = gradient(B, [n, m])

Script

X0 = [...];

fhandle = @myfun;

X = fsolve(fhandle, X0)

Answer 1

[Star Strider]

It’s a bit difficult to follow what you’re doing, but if you want to use symbolic expressions and you don’t mind slow code, use the solve function.

the fsolve function will find the values where the argument function equates to zero, so if you want to do the same with your symbolic gradient, my answer to Finding the null gradient directly applies to your problem.

[bh1910]

I'll try that. Thanks

[Star Strider]

My pleasure.

It seems to have worked in my other Answer.

[Walter Roberson]

You should consider vpasolve() instead of solve(). solve() will try to find closed-form solutions; vpasolve() will look for numeric solutions.

[bh1910]

Tks Walter

[bh1910]

vpasolve did the job!

[safi58]

Hi Can you please post the code with vpasolve. thanks