English
The inverse of the ε-iso on the free generator applied to a unit gives the freeMk of that unit.
Русский
Обратное ε-изоморфизма на свободном генераторе, применённое к единице, даёт свободный элемент свободного модуля.
LaTeX
$$$(\epsilonIso\,R)^{\mathrm{inv}}(\mathrm{freeMk}(x)) = 1$$$
Lean4
/-- The canonical isomorphism `(free R).obj X ⊗ (free R).obj Y ≅ (free R).obj (X ⊗ Y)`
for two types `X` and `Y`.
(This should not be used directly: it is part of the implementation of the
monoidal structure on the functor `free R`.) -/
def μIso (X Y : Type u) : (free R).obj X ⊗ (free R).obj Y ≅ (free R).obj (X ⊗ Y) :=
(finsuppTensorFinsupp' R _ _).toModuleIso