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Metamath Proof Explorer

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	$⊢ φ \to (ψ \to (ψ \land φ))$

Step	Hyp	Ref	Expression
1		id	$⊢ (ψ \land φ) \to (ψ \land φ)$
2	1	expcom	$⊢ φ \to (ψ \to (ψ \land φ))$