Hi Florent, It would be better to open a GitHub issue with this as it is a bug.
The output should be None in both cases rather than True or False because it is possible that X*Z is symmetric (for example if X and Z are diagonal) but also possible that it is not. Thanks, Oscar On Mon, 13 Oct 2025 at 19:54, Florent Périat <[email protected]> wrote: > > Hi everyone, > > I just read the documentation and noticed that there is, as I understood it, > a mathematical mistake (and also at the execution). > > If you look at this section, it seems to assert that the product (not the > Hadamard product, but usual one) of two symmetric matrices is also symmetric, > which is True if and only if both matrices commutes; but as their shape is > (in the example) defined as 2x2, they do not necessarily. > > from sympy import Q, ask, MatrixSymbol, Equality > > X = MatrixSymbol('X', 2, 2) > Z = MatrixSymbol('Z', 2, 2) > > print(ask(Q.symmetric(X * Z), Q.symmetric(X) & Q.symmetric(Z))) # True > print(ask(Equality(X * Z, Z * X), Q.symmetric(X) & Q.symmetric(Z))) # False > > Here both output should give False. > > Best regards, > > F. Périat > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/sympy/d029d408-66cb-4531-a548-b7e455a0387dn%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/sympy/CAHVvXxQo%2BpdFPBrE9X6n2L%3DRVDiZ%2B4G8_OSQ33EUGnWHuVfRvQ%40mail.gmail.com.
