Theorem pm4.25 911

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 910	. 2 ⊢ ((𝜑 ∨ 𝜑) ↔ 𝜑)
2	1	bicomi 225	1 ⊢ (𝜑 ↔ (𝜑 ∨ 𝜑))

Syntax hints:   ↔ wb 207   ∨ wo 853

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 208  df-or 854

This theorem is referenced by:  elOLD  5378  brbtwn2  28992  ifpid1g  43938  uneqsn  44469  homf0  49499