English
If two representations are equal as matrices with respect to b, then their action on coordinates agrees with f and f′ respectively on corresponding coordinate vectors.
Русский
Если две записи совпадают, то их действие на координаты согласуется с соответствующими отображениями f и f′.
LaTeX
$$Same content as 130206, expressed as a congruence statement with two representations.$$
Lean4
theorem congr_fun {A : Matrix ι ι R} {f : Module.End R M} (h : A.Represents b f) (x) :
Fintype.linearCombination R b (A *ᵥ x) = f (Fintype.linearCombination R b x) :=
LinearMap.congr_fun h x