English
The inverse of the lTensor equivalence composed with lTensor g equals the mkQ map, i.e., the canonical projection onto the quotient by range(f).
Русский
Обратный к композиции левого тензорного эквивалента совпадает с проекцией на квотируемый модуль по образу f.
LaTeX
$$inverse_comp_lTensor : (lTensor.inverse Q hfg hg).comp (lTensor Q g) = Submodule.mkQ (p := LinearMap.range (lTensor Q f))$$
Lean4
theorem inverse_of_rightInverse_comp_rTensor {h : P → N} (hgh : Function.RightInverse h g) :
(rTensor.inverse_of_rightInverse Q hfg hgh).comp (rTensor Q g) =
Submodule.mkQ (p := LinearMap.range (rTensor Q f)) :=
by
rw [LinearMap.ext_iff]
intro y
simp only [coe_comp, Function.comp_apply, Submodule.mkQ_apply, rTensor.inverse_of_rightInverse_apply]