Let a be given.
We prove the intermediate
claim Haeq:
a = 0.
An
exact proof term for the current goal is
(SingE 0 a Ha0).
rewrite the current goal using Haeq (from left to right).
Let j0 be given.
We prove the intermediate
claim Hj0R:
apply_fun f j0 ∈ R.
rewrite the current goal using H0eq (from right to left).
∎