Let X, Tx, A, B and C be given.
Let x be given.
Apply HexAB to the current goal.
Let a be given.
Assume HexB.
Apply HexB to the current goal.
Let b be given.
Assume HabPack.
Assume HaA HbB HaComp HbComp.
Apply HexW to the current goal.
Let W be given.
Assume HWpack.
We prove the intermediate
claim HexcW:
∃cW : set, cW ∈ C ∧ cW ∈ W.
An exact proof term for the current goal is (Hchoice W HWcomp HWend).
Apply HexcW to the current goal.
Let cW be given.
Assume HcWpack.
We prove the intermediate
claim HcWC:
cW ∈ C.
An
exact proof term for the current goal is
(andEL (cW ∈ C) (cW ∈ W) HcWpack).
We prove the intermediate
claim HcWW:
cW ∈ W.
An
exact proof term for the current goal is
(andER (cW ∈ C) (cW ∈ W) HcWpack).
An exact proof term for the current goal is (HWsub cW HcWW).
We prove the intermediate
claim HcWY:
cW ∈ (X ∖ C).
We prove the intermediate
claim HcWnotC:
cW ∉ C.
An
exact proof term for the current goal is
(setminusE2 X C cW HcWY).
An exact proof term for the current goal is (HcWnotC HcWC).
∎