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Metamath Proof Explorer

Theorem pm2.38

Description: Theorem *2.38 of WhiteheadRussell p. 105. (Contributed by NM, 6-Mar-2008)

		Ref	Expression
	Assertion	pm2.38	$⊢ (ψ \to χ) \to ((ψ \lor φ) \to (χ \lor φ))$

Step	Hyp	Ref	Expression
1		id	$⊢ (ψ \to χ) \to (ψ \to χ)$
2	1	orim1d	$⊢ (ψ \to χ) \to ((ψ \lor φ) \to (χ \lor φ))$