Dear Matlab Community, While doing a solution with MATLAB, I got 2 nonlinear equations, say, eqn1 and eqn2 generated with two variables and in output. The size of equations are large (got as output). How can I use "fsolve" for solving them without copying them from the output and without setting x(1) and x(2) but defining and ?

fsolve for generated equations

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Aniket Roy 2021-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/845180-fsolve-for-generated-equations

评论： Star Strider 2021-6-9

采纳的回答： Star Strider

Dear Matlab Community,

While doing a solution with MATLAB, I got 2 nonlinear equations, say, eqn1 and eqn2 generated with two variables s and t in output. The size of equations are large (got as output). How can I use "fsolve" for solving them without copying them from the output and without setting x(1) and x(2) but defining

and

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Star Strider 2021-6-1

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https://ww2.mathworks.cn/matlabcentral/answers/845180-fsolve-for-generated-equations#answer_714335

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Having the equations themselves would hellp.

However assuming they are something like this:

y1 = s.^2 + 10*t;

y2 = 10*s + t.^1/3;

I would code them as:

y1 = @(s,t) s.^2 + 10*t;
y2 = @(s,t) 10*s + t.^1/3;

then:

X = fsolve(@(x) [y1(x(1),x(2)); y2(x(1),x(2))], [3 9])
Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.
X = 1×2
	1.0e+-13 *

   -0.0099    0.2960