English
Let M,N,P be square matrices over a commutative ring R. Then det(M(NP)) = det(N(MP)).
Русский
Пусть M,N,P — квадратные матрицы над коммутативной кольцевой R. Тогда det(M(NP)) = det(N(MP)).
LaTeX
$$$$\det(M(NP)) = \det(N(MP))$$$$
Lean4
/-- On square matrices, `mul_right_comm` applies under `det`. -/
theorem det_mul_right_comm (M N P : Matrix m m R) : det (M * N * P) = det (M * P * N) := by
rw [Matrix.mul_assoc, Matrix.mul_assoc, det_mul, det_mul_comm N P, ← det_mul]
-- TODO(https://github.com/leanprover-community/mathlib4/issues/6607): fix elaboration so `val` isn't needed