Let X, Tx, A, seq and x be given.
We prove the intermediate
claim Hxcl:
x ∈ closure_of X Tx A.
We prove the intermediate
claim HclEq:
closure_of X Tx A = A.
rewrite the current goal using HclEq (from right to left).
An exact proof term for the current goal is Hxcl.
∎