Let t1 be given.
Let t2 be given.
rewrite the current goal using Hf1 (from right to left) at position 1.
rewrite the current goal using Hf2 (from right to left) at position 1.
rewrite the current goal using Heq (from left to right) at position 1.
Use reflexivity.
rewrite the current goal using Hpsi1 (from right to left).
rewrite the current goal using Hpsi2 (from right to left).
rewrite the current goal using HphiEq (from left to right).
Use reflexivity.
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