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| Description: Inference that swaps (commutes) antecedents in an implication. |
| Ref | Expression |
|---|---|
| comm.1 |
|
| Ref | Expression |
|---|---|
| com12 |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | ax-1 3 |
. 2
| |
| 2 | comm.1 |
. . 3
| |
| 3 | 2 | a2i 8 |
. 2
|
| 4 | 1, 3 | syl 12 |
1
|