Theorem pm4.39 841

Description: Theorem *4.39 of [WhiteheadRussell] p. 118. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm4.39	⊢ (((φ ↔ χ) ∧ (ψ ↔ θ)) → ((φ ∨ ψ) ↔ (χ ∨ θ)))

Proof of Theorem pm4.39

Step	Hyp	Ref	Expression
1		simpl 443	. 2 ⊢ (((φ ↔ χ) ∧ (ψ ↔ θ)) → (φ ↔ χ))
2		simpr 447	. 2 ⊢ (((φ ↔ χ) ∧ (ψ ↔ θ)) → (ψ ↔ θ))
3	1, 2	orbi12d 690	1 ⊢ (((φ ↔ χ) ∧ (ψ ↔ θ)) → ((φ ∨ ψ) ↔ (χ ∨ θ)))

Syntax hints:   → wi 4   ↔ wb 176   ∨ wo 357   ∧ wa 358

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 177  df-or 359  df-an 360

This theorem is referenced by: (None)