English
If x is W-equivalent to y, then y is W-equivalent to x.
Русский
Если x эквивалентен y по WEquiv, то y эквивалентен x.
LaTeX
$$$\forall {\alpha : TypeVec n} (x y : (q.P F).W \alpha), WEquiv x y \Rightarrow WEquiv y x$$$
Lean4
theorem symm {α : TypeVec n} (x y : q.P.W α) : WEquiv x y → WEquiv y x := by intro h;
induction h with
| ind a f' f₀ f₁ _h ih => exact WEquiv.ind _ _ _ _ ih
| abs a₀ f'₀ f₀ a₁ f'₁ f₁ h => exact WEquiv.abs _ _ _ _ _ _ h.symm
| trans x y z _e₁ _e₂ ih₁ ih₂ => exact MvQPF.WEquiv.trans _ _ _ ih₂ ih₁