Theorem bitr 817

Description: Theorem *4.22 of [WhiteheadRussell] p. 117. bitri 278 in closed form. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
bitr	⊢ (((𝜑 ↔ 𝜓) ∧ (𝜓 ↔ 𝜒)) → (𝜑 ↔ 𝜒))

Proof of Theorem bitr

Step	Hyp	Ref	Expression
1		bibi1 354	. 2 ⊢ ((𝜑 ↔ 𝜓) → ((𝜑 ↔ 𝜒) ↔ (𝜓 ↔ 𝜒)))
2	1	biimpar 483	1 ⊢ (((𝜑 ↔ 𝜓) ∧ (𝜓 ↔ 𝜒)) → (𝜑 ↔ 𝜒))

This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401

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

This proof depends on definitions:  df-bi 210  df-an 402

This theorem is used by:  opelopabt  5506  domunfican  9297  albitr  45306  3orbi123VD  45791  e2ebindALT  45870