have := h ▸ selection x
X : Type u_1
inst✝ : OrientableInvolutiveInv X
x x' : X
h : pos x = true
⊢ ¬pos x⁻¹ = true
X : Type u_1
inst✝ : OrientableInvolutiveInv X
x x' : X
h : pos x = true
this : xor true (pos x⁻¹) = true
⊢ ¬pos x⁻¹ = true