Jordan power-associativity: (X²)∘X = X∘(X²) = X³ on Sym_2(R)

On Sym_2(R) (symmetric 2×2 real matrices with Jordan product A∘B = (AB + BA)/2) the power-associativity identity X²∘X = X∘X² reduces to 0 via straightforward expansion since X and X² commute in the associative parent matrix algebra. Sympy…