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Metamath Proof Explorer

Theorem n0i

Description: If a class has elements, then it is not empty. (Contributed by NM, 31-Dec-1993)

Ref Expression
Assertion n0i 
|- ( B e. A -> -. A = (/) )

Proof

Step Hyp Ref Expression
1 nel02 
 |-  ( A = (/) -> -. B e. A )
2 1 con2i 
 |-  ( B e. A -> -. A = (/) )