Let m, n and k be given.
Apply H1 to the current goal.
Assume H.
Apply H to the current goal.
Assume H.
Apply H to the current goal.
Let l be given.
Assume H.
Apply H to the current goal.
Apply and3I to the current goal.
An exact proof term for the current goal is Hm.
An exact proof term for the current goal is Hn.
An exact proof term for the current goal is Hk.
We use
l * k to
witness the existential quantifier.
Apply andI to the current goal.
We will
prove l * k ∈ int.
An exact proof term for the current goal is Hl.
An exact proof term for the current goal is Hk.
We will
prove m * (l * k) = n * k.
We will
prove (m * l) * k = n * k.
Use f_equal.
An exact proof term for the current goal is H2.
∎