Description: Biconditional for equivalent elements. (Contributed by Thierry Arnoux, 6-Jan-2020)
Ref | Expression | ||
---|---|---|---|
Assertion | erbr3b |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | simpll | ||
2 | simplr | ||
3 | simpr | ||
4 | 1 2 3 | ertr3d | |
5 | simpll | ||
6 | simplr | ||
7 | simpr | ||
8 | 5 6 7 | ertrd | |
9 | 4 8 | impbida |