nf4 - Metamath Proof Explorer

	Metamath Proof Explorer		< Previous Next > Nearby theorems
Mirrors > Home > MPE Home > Th. List > nf4		Structured version Visualization version Unicode version

Theorem nf4 1713

Description: Alternate definition of non-freeness. This definition uses only primitive symbols. (Contributed by BJ, 16-Sep-2021.)

**Assertion**
Ref	Expression
nf4

**Proof of Theorem nf4**
Step	Hyp	Ref	Expression
1		nf3 1712	. 2 $\/$
2		df-or 385	. 2 $\/$
3	1, 2	bitri 264	1

Colors of variables: wff setvar class

Syntax hints:

wn 3

wi 4

wb 196 $\/$ wo 383

wal 1481

wnf 1708

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 197 df-or 385 df-ex 1705 df-nf 1710

This theorem is referenced by: nfimdOLDOLD 1824