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Metamath Proof Explorer

Theorem preq2i

Description: Equality inference for unordered pairs. (Contributed by NM, 19-Oct-2012)

Ref Expression
Hypothesis preq1i.1 ⊢ A = B
Assertion preq2i ⊢ C A = C B

Proof

Step Hyp Ref Expression
1 preq1i.1 ⊢ A = B
2 preq2 ⊢ A = B → C A = C B
3 1 2 ax-mp ⊢ C A = C B