refine' ⟨_, h⟩
case inl
X : Type u_1
inst✝ : ProperInvolutiveInv X
x : X
h : x ∉ ↑(maxInvFreeSet X)
⊢ ¬x = x⁻¹ ∧ x ∉ ↑(maxInvFreeSet X)
case inl
X : Type u_1
inst✝ : ProperInvolutiveInv X
x : X
h : x ∉ ↑(maxInvFreeSet X)
⊢ ¬x = x⁻¹