Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι → ι be given.
Let x3 of type ι → ι be given.
Let x4 of type ι be given.
Let x5 of type ι be given.
Assume H1: x5 ∈ x1.
Apply H0 with
λ x6 x7 . x2 x5 = ap (ap x7 1) x5.
Apply tuple_4_1_eq with
x1,
lam x1 x2,
lam x1 x3,
x4,
λ x6 x7 . x2 x5 = ap x7 x5.
Let x6 of type ι → ι → ο be given.
Apply beta with
x1,
x2,
x5,
λ x7 x8 . x6 x8 x7.
The subproof is completed by applying H1.