MATLAB: Solve returns empty result although solution exists

solveSymbolic Math Toolbox

Hello I'm trying to solve the following system of equations,

This should be easy to solve by hand. However using solve returns an empty sym struct. what am i missing here?

variables used are attached.

Thank you.

EDIT: re-uploaded variables and added code.

EDIT2:provided working example as per @Walter Roberson's comment.

Best Answer

You are accidentally using Maple's sym() and solve() calls. The .mat you provided for us is only useable by people who have installed "MATLAB Connector for Maple" .

You need to use pathtool to give the Maple functions a lower priority than the MATLAB functions and recreate the equations matrix and try again.

Related Solutions

MATLAB: Solving Diophantine Equations in MATLAB

Use the “solve” function. Before using “solve”, assume that the variables in the Diophantine equation are integers to ensure “solve” returns integer solutions. For example, solve the linear Diophantine equation 1027*x + 712*y = 1;

For MATLAB R2015a and later:

syms x y integer                % assume ‘x’ and ‘y’ are integers

eqn = 1027*x + 712*y == 1;       % declare the equation

[xSol, ySol] = solve(eqn,[x y])  % solve for ‘x’ and ‘y’

xSol =
-165
ySol =
238

For MATLAB R2014b or before:

syms x y
assume([x y], 'integer')        % assume ‘x’ and ‘y’ are integers
eqn = 1027*x + 712*y == 1;       % declare the equation
[xSol, ySol] = solve(eqn,[x y])  % solve for ‘x’ and ‘y’
xSol =
-165
ySol =
238

For details on “solve”, see: https://www.mathworks.com/help/symbolic/solve.html

For more information on assumptions, see: https://www.mathworks.com/help/symbolic/assumptions-for-symbolic-objects.html

MATLAB: Program Sudden Errors Appearing

You installed Maple after you installed MATLAB, and you gave permission for Maple to install the Maple Symbolic Toolbox for MATLAB, which defines sym() and solve() and some other routines but uses symbolic equations differently than MATLAB's Symbolic Toolbox does. Your code defines eqn1 and eqn2 using the form

eqn1 = one_expression == another_expression

which is valid in MATLAB's Symbolic Toolbox meaning "construct a symbolic expression with two parts joined by the "==" operator that can be reasoned about later." When you have Maple's symbolic toolbox, this is instead interpreted as "test now whether the two expressions are exactly the same and assign logical false to eqn1 now if they are different and logical true to eqn1 now if they are the same".

The solution is to either remove the Maple symbolic toolbox for MATLAB, or else to use pathtool to push it down to lower priority than MATLAB's Symbolic Toolbox.

Best Answer

Related Solutions

MATLAB: Solving Diophantine Equations in MATLAB

MATLAB: Program Sudden Errors Appearing

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