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| Description: A mixed syllogism inference from a nested implication and a biconditional. Useful for substituting an embedded antecedent with a definition. |
| Ref | Expression |
|---|---|
| syl5ib.1 |
|
| syl5ib.2 |
|
| Ref | Expression |
|---|---|
| syl5ib |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | syl5ib.1 |
. 2
| |
| 2 | syl5ib.2 |
. . 3
| |
| 3 | 2 | biimp 151 |
. 2
|
| 4 | 1, 3 | syl5 21 |
1
|