Let x0 of type ι → ι be given.
Let x1 of type ι → ι be given.
Let x2 of type ι → ι be given.
Assume H0:
not (x0 = x1).
Assume H1:
not (x0 = x2).
Assume H2:
not (x1 = x2).
Assume H3:
f8922.. (λ x3 : ι → ι . or (or (x3 = x0) (x3 = x1)) (x3 = x2)).
Let x3 of type ι be given.
Apply andER with
9a7b4.. x0 x1 x3,
9a7b4.. x0 x2 x3.
The subproof is completed by applying H4.