Theorem frege61a 40218

Description: Lemma for frege65a 40222. Proposition 61 of [Frege1879] p. 52. (Contributed by RP, 17-Apr-2020.) (Proof modification is discouraged.)

Assertion

Ref	Expression
frege61a	⊢ ((if-(𝜑, 𝜓, 𝜒) → 𝜃) → ((𝜓 ∧ 𝜒) → 𝜃))

Proof of Theorem frege61a

Step	Hyp	Ref	Expression
1		ax-frege58a 40214	. 2 ⊢ ((𝜓 ∧ 𝜒) → if-(𝜑, 𝜓, 𝜒))
2		frege9 40151	. 2 ⊢ (((𝜓 ∧ 𝜒) → if-(𝜑, 𝜓, 𝜒)) → ((if-(𝜑, 𝜓, 𝜒) → 𝜃) → ((𝜓 ∧ 𝜒) → 𝜃)))
3	1, 2	ax-mp 5	1 ⊢ ((if-(𝜑, 𝜓, 𝜒) → 𝜃) → ((𝜓 ∧ 𝜒) → 𝜃))

Syntax hints:   → wi 4   ∧ wa 398  if-wif 1057

This theorem was proved from axioms:  ax-mp 5  ax-frege1 40129  ax-frege2 40130  ax-frege8 40148  ax-frege58a 40214

This theorem is referenced by:  frege65a  40222