This question is motivated by another one I recently asked: Obstacle problem for the heat equation.

It seems to me that


does not work for differential inequalities (or systems of differential inequalities). Indeed, I get an error of the type: "a differential equation was expected in the input".

What command does one use to solve mixed systems of differential equations and differential inequalities?

  • $\begingroup$ @bbgodfrey So it doesn't depend on the fact that I've a differential inequality instead of a differential equation? $\endgroup$
    – user51360
    Commented Jul 29, 2017 at 18:51
  • $\begingroup$ I see that I misread your question. Sorry. NDSolve probably is objecting to the inequalities. $\endgroup$
    – bbgodfrey
    Commented Jul 29, 2017 at 18:53

1 Answer 1


DSolveValue doesn't support differential inequalities, as they don't tend to produce any sort of easily writable "solutions". It would be the function to use, however, if we did have support (Just as Solve works for both equations and inequalities). If you would like this feature, I suggest contacting support and requesting it, who will then pass it along to the relevant developers. Some indication of the scope of what you would want from this functionality is probably in order for this topic.


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