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| Description: Inference derived from axiom ax-1 4. See a1d 12 for an explanation of our informal use of the terms "inference" and "deduction." |
| Ref | Expression |
|---|---|
| a1i.1 |
|
| Ref | Expression |
|---|---|
| a1i |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | a1i.1 |
. 2
| |
| 2 | ax-1 4 |
. 2
| |
| 3 | 1, 2 | ax-mp 7 |
1
|