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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 
|- ( ph -> A = A )

Proof

Step Hyp Ref Expression
1 eqid 
 |-  A = A
2 1 a1i 
 |-  ( ph -> A = A )