Theorem frege58acor 44724

Description: Lemma for frege59a 44725. (Contributed by RP, 17-Apr-2020.) (Proof modification is discouraged.)

Assertion

Ref	Expression
frege58acor	⊢ (((𝜓 → 𝜒) ∧ (𝜃 → 𝜏)) → (if-(𝜑, 𝜓, 𝜃) → if-(𝜑, 𝜒, 𝜏)))

Proof of Theorem frege58acor

Step	Hyp	Ref	Expression
1		ax-frege58a 44723	. 2 ⊢ (((𝜓 → 𝜒) ∧ (𝜃 → 𝜏)) → if-(𝜑, (𝜓 → 𝜒), (𝜃 → 𝜏)))
2		ifpimim 44357	. 2 ⊢ (if-(𝜑, (𝜓 → 𝜒), (𝜃 → 𝜏)) → (if-(𝜑, 𝜓, 𝜃) → if-(𝜑, 𝜒, 𝜏)))
3	1, 2	syl 18	1 ⊢ (((𝜓 → 𝜒) ∧ (𝜃 → 𝜏)) → (if-(𝜑, 𝜓, 𝜃) → if-(𝜑, 𝜒, 𝜏)))

This proof depends on syntax axioms:   → wi 4   ∧ wa 401  if-wif 1078

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-frege58a 44723

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-ifp 1079

This theorem is used by:  frege59a  44725  frege60a  44726  frege62a  44728