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Description: Commutation of antecedents. Swap 2nd and 4th. Deduction associated with com13 . (Contributed by NM, 25-Apr-1994) (Proof shortened by Wolf Lammen, 28-Jul-2012)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | com4.1 | ||
| Assertion | com24 |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | com4.1 | ||
| 2 | 1 | com4t | |
| 3 | 2 | com13 |