Description: Join antecedents with conjunction. Theorem *3.21 of WhiteheadRussell p. 111. (Contributed by NM, 5-Aug-1993)
Ref | Expression | ||
---|---|---|---|
Assertion | pm3.21 | ⊢ ( 𝜑 → ( 𝜓 → ( 𝜓 ∧ 𝜑 ) ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | id | ⊢ ( ( 𝜓 ∧ 𝜑 ) → ( 𝜓 ∧ 𝜑 ) ) | |
2 | 1 | expcom | ⊢ ( 𝜑 → ( 𝜓 → ( 𝜓 ∧ 𝜑 ) ) ) |