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Description: Theorem *4.81 of [WhiteheadRussell] p. 122. |
Ref | Expression |
---|---|
pm4.81 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pm2.18 101 | . 2 | |
2 | pm2.24 100 | . 2 | |
3 | 1, 2 | impbii 178 | 1 |
Colors of variables: wff set class |
Syntax hints: wn 3 wi 4 wb 174 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-3 7 ax-mp 8 |
This theorem depends on definitions: df-bi 175 |