Theorem pm4.25 902

Description: Theorem *4.25 of [WhiteheadRussell] p. 117. (Contributed by NM, 3-Jan-2005.)

Assertion

Ref	Expression
pm4.25	⊢ (𝜑 ↔ (𝜑 ∨ 𝜑))

Proof of Theorem pm4.25

Step	Hyp	Ref	Expression
1		oridm 901	. 2 ⊢ ((𝜑 ∨ 𝜑) ↔ 𝜑)
2	1	bicomi 223	1 ⊢ (𝜑 ↔ (𝜑 ∨ 𝜑))

Syntax hints:   ↔ wb 205   ∨ wo 843

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 206  df-or 844

This theorem is referenced by:  brbtwn2  27176  ifpid1g  40999  uneqsn  41522