English
A cyclic commutativity property: tr(g∘f) = tr(f∘g) for suitable endomorphisms f,g.
Русский
Циклическое свойство следа: tr(g∘f) = tr(f∘g) для подходящих концевых отображений.
LaTeX
$$$ \operatorname{trace}_R M (g \circ f) = \operatorname{trace}_R N (f \circ g). $$$
Lean4
theorem trace_tensorProduct' (f : M →ₗ[R] M) (g : N →ₗ[R] N) : trace R (M ⊗ N) (map f g) = trace R M f * trace R N g :=
by
have h := LinearMap.ext_iff.1 (LinearMap.ext_iff.1 (trace_tensorProduct R M N) f) g
simp only [compr₂_apply, mapBilinear_apply, compl₁₂_apply, lsmul_apply, Algebra.id.smul_eq_mul] at h
exact h