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Description: Join antecedents with conjunction. Theorem *3.21 of WhiteheadRussell p. 111. (Contributed by NM, 5-Aug-1993)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | pm3.21 | |- ( ph -> ( ps -> ( ps /\ ph ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | id | |- ( ( ps /\ ph ) -> ( ps /\ ph ) ) |
|
| 2 | 1 | expcom | |- ( ph -> ( ps -> ( ps /\ ph ) ) ) |