Theorem pm2.43b 46

Description: Inference absorbing redundant antecedent. (Contributed by NM, 31-Oct-1995.)

Hypothesis

Ref	Expression
pm2.43b.1	⊢ (ψ → (φ → (ψ → χ)))

Assertion

Ref	Expression
pm2.43b	⊢ (φ → (ψ → χ))

Proof of Theorem pm2.43b

Step	Hyp	Ref	Expression
1		pm2.43b.1	. . 3 ⊢ (ψ → (φ → (ψ → χ)))
2	1	pm2.43a 45	. 2 ⊢ (ψ → (φ → χ))
3	2	com12 27	1 ⊢ (φ → (ψ → χ))

Syntax hints:   → wi 4

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7

This theorem is referenced by:  ncfinlower  4484  funfvima  5460