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Theorem biorfi 396

Description: A wff is equivalent to its disjunction with falsehood. (Contributed by NM, 23-Mar-1995.)

**Hypothesis**
Ref	Expression
biorfi.1

**Assertion**
Ref	Expression
biorfi	$\/$

**Proof of Theorem biorfi**
Step	Hyp	Ref	Expression
1		biorfi.1	. 2
2		orc 374	. . 3 $\/$
3		orel2 372	. . 3 $\/$
4	2, 3	impbid2 195	. 2 $\/$
5	1, 4	ax-mp 8	1 $\/$

Colors of variables: wff setvar class

Syntax hints:

wn 3

wb 176 $\/$ wo 357

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

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

This theorem is referenced by: pm4.43 893 dn1 932 indifdir 3511 un0 3575 eqtfinrelk 4486 proj1op 4600 proj2op 4601 imadif 5171