Theorem pm2.43a

Description: Inference absorbing redundant antecedent. (Contributed by NM, 7-Nov-1995) (Proof shortened by Mel L. O'Cat, 28-Nov-2008)

	Ref	Expression
Hypothesis	pm2.43a.1	⊢ ( 𝜓 → ( 𝜑 → ( 𝜓 → 𝜒 ) ) )
Assertion	pm2.43a	⊢ ( 𝜓 → ( 𝜑 → 𝜒 ) )

Proof

Step	Hyp	Ref	Expression
1		pm2.43a.1	⊢ ( 𝜓 → ( 𝜑 → ( 𝜓 → 𝜒 ) ) )
2		id	⊢ ( 𝜓 → 𝜓 )
3	2 1	mpid	⊢ ( 𝜓 → ( 𝜑 → 𝜒 ) )