Has solve() changed its behaviour if the solution to the equation is all real numbers?

Question

Andreas 2015-7-14

回答： Ghada Saleh 2015-7-16

Hello,

to test a real function for special symmetry (See if it is even or odd) with the Matlab Symbolic Math Toolbox I have used the following code:

syms x real;
f(x) = x^2;
solve(f(x) == f(-x), x)

Expected result is

R_

Which is as far as I understand the Mupad Syntax for all real numbers. This Result was given until and including release R2014a.

From release R2014b on, I just get

0

which is obviously one single solution, but not all solutions to the equation.

In the release notes I did not see anything interesting about solve.

Answer 1

Ghada Saleh 2015-7-16

Hi Andreas,

This is an issue in MATLAB R2014b and later versions. As a workaround you can use the following command:

[solx param cond] = solve(f(x) == f(-x), x, 'ReturnConditions', true)

I hope this helps.

Ghada