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Metamath Proof Explorer

Theorem eqidd

Description: Class identity law with antecedent. (Contributed by NM, 21-Aug-2008)

Ref Expression
Assertion eqidd ( 𝜑 → 𝐴 = 𝐴 )

Proof

Step Hyp Ref Expression
1 eqid ⊢ 𝐴 = 𝐴
2 1 a1i ⊢ ( 𝜑 → 𝐴 = 𝐴 )