Let L and R be given.
Apply HLR to the current goal.
Assume H.
Apply H to the current goal.
Set Lm to be the term
{- z|z ∈ R}.
Set Rm to be the term
{- w|w ∈ L}.
Apply and3I to the current goal.
Let w be given.
Let z be given.
rewrite the current goal using Hwz (from left to right).
Apply HLR2 to the current goal.
An exact proof term for the current goal is Hz.
Let z be given.
Let w be given.
rewrite the current goal using Hzw (from left to right).
An exact proof term for the current goal is HLR1 w Hw.
Let w be given.
Let z be given.
Let u be given.
Let v be given.
rewrite the current goal using Hwu (from left to right).
rewrite the current goal using Hzv (from left to right).
An exact proof term for the current goal is HLR3 v Hv u Hu.
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