English
The word of the inverse in the free group is the inverse-reverse of the word: toWord(x^{-1}) = invRev(toWord x).
Русский
Слово обратного элемента в свободной группе равно развёрнутому слову: toWord(x^{-1}) = invRev(toWord x).
LaTeX
$$$\forall x : FreeGroup\,\alpha ,\; x^{-1}.toWord = invRev(x.toWord)$$$
Lean4
@[to_additive (attr := simp)]
theorem toWord_inv (x : FreeGroup α) : x⁻¹.toWord = invRev x.toWord :=
by
rcases x with ⟨L⟩
rw [quot_mk_eq_mk, inv_mk, toWord_mk, toWord_mk, reduce_invRev]