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 | $${\u22a2}{A}\approx {B}\to {B}\approx {A}$$ |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ensymb | $${\u22a2}{A}\approx {B}\leftrightarrow {B}\approx {A}$$ | |
2 | 1 | biimpi | $${\u22a2}{A}\approx {B}\to {B}\approx {A}$$ |