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Mirrors > Home > ILE Home > Th. List > 19.31r | Unicode version |
Description: One direction of Theorem 19.31 of [Margaris] p. 90. The converse holds in classical logic, but not intuitionistic logic. (Contributed by Jim Kingdon, 28-Jul-2018.) |
Ref | Expression |
---|---|
19.31r.1 |
Ref | Expression |
---|---|
19.31r |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 19.31r.1 | . . 3 | |
2 | 1 | 19.32r 1610 | . 2 |
3 | orcom 679 | . 2 | |
4 | orcom 679 | . . 3 | |
5 | 4 | albii 1399 | . 2 |
6 | 2, 3, 5 | 3imtr4i 199 | 1 |
Colors of variables: wff set class |
Syntax hints: wi 4 wo 661 wal 1282 wnf 1389 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-io 662 ax-5 1376 ax-gen 1378 ax-4 1440 |
This theorem depends on definitions: df-bi 115 df-nf 1390 |
This theorem is referenced by: (None) |
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