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