Metamath Proof Explorer

Theorem ensym

Description: Symmetry of equinumerosity. Theorem 2 of Suppes p. 92. (Contributed by NM, 26-Oct-2003) (Revised by Mario Carneiro, 26-Apr-2015)

Ref Expression
Assertion ensym 
|- ( A ~~ B -> B ~~ A )

Proof

Step Hyp Ref Expression
1 ensymb 
 |-  ( A ~~ B <-> B ~~ A )
2 1 biimpi 
 |-  ( A ~~ B -> B ~~ A )