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| Description: Theorem *2.62 of [WhiteheadRussell] p. 107. |
| Ref | Expression |
|---|---|
| pm2.62 |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | dfor2 199 |
. 2
| |
| 2 | 1 | biimp 133 |
1
|
| Colors of variables: wff set class |
| Syntax hints: |
| This theorem is referenced by: pm2.621 211 |
| This theorem was proved from axioms: ax-1 3 ax-2 4 ax-3 5 ax-mp 6 |
| This theorem depends on definitions: df-bi 128 df-or 197 |