Theorem pm3.21

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 ) ) )

Proof

Step	Hyp	Ref	Expression
1		id	⊢ ( ( 𝜓 ∧ 𝜑 ) → ( 𝜓 ∧ 𝜑 ) )
2	1	expcom	⊢ ( 𝜑 → ( 𝜓 → ( 𝜓 ∧ 𝜑 ) ) )