Solve a system of two variable inequalities with symbolic toolbox

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LUCA D'AMBROSIO
LUCA D'AMBROSIO 2024-7-1
评论： LUCA D'AMBROSIO 2024-7-2
Hello,
is it possible to symbolically solve a system of inequalities with variables x and y and plot the result?
lets say i have to solve x+y-25>0 and x*y+y+15>0, what function should i use?
i have tried fimplicit plus assumptions but it didn't work.
thank you

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John D'Errico
John D'Errico 2024-7-1
Ran in:
fimplicit does not plot inequalities. Sorry. If you read the help, it never says anything about inequalities.
Simplest is to just use meshgrid. For example...
[X,Y] = meshgrid(linspace(-50,50,1000));
k = (X + Y - 25 > 0) & (X.*Y + Y + 15 > 0);
plot(X(k),Y(k),'.')
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LUCA D'AMBROSIO
LUCA D'AMBROSIO 2024-7-2
hi, sorry to bother you, thank you for your answer.
do you know if there is a way to extract only the boundary of the region highlighted in the figure? i figured i don't need all the points where both inequalities are satisfied but only the curve where they are equal to zero, so the boundary and i need to check how this boundary evolves with some variyng constants.
thank you for your help

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Torsten
Torsten 2024-7-1
移动：Torsten 2024-7-1
is it possible to symbolically solve a system of inequalities with variables x and y ?
What do you mean by "solve" ? The feasible set is given by the set of inequalities, and in most cases it is not possible to find an easier representation.

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