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Mirrors > Home > MPE Home > Th. List > df-sgn | Structured version Visualization version Unicode version |
Description: Signum function. Pronounced "signum" , otherwise it might be confused with "sine". Defined as "sgn" in ISO 80000-2:2009(E) operation 2-9.13. It is named "sign" (with the same definition) in the "NIST Digital Library of Mathematical Functions" , front introduction, "Common Notations and Definitions" section at http://dlmf.nist.gov/front/introduction#Sx4. We define this over (df-xr 10078) instead of so that it can accept and . Note that df-psgn 17911 defines the sign of a permutation, which is different. Value shown in sgnval 13828. (Contributed by David A. Wheeler, 15-May-2015.) |
Ref | Expression |
---|---|
df-sgn | sgn |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | csgn 13826 | . 2 sgn | |
2 | vx | . . 3 | |
3 | cxr 10073 | . . 3 | |
4 | 2 | cv 1482 | . . . . 5 |
5 | cc0 9936 | . . . . 5 | |
6 | 4, 5 | wceq 1483 | . . . 4 |
7 | clt 10074 | . . . . . 6 | |
8 | 4, 5, 7 | wbr 4653 | . . . . 5 |
9 | c1 9937 | . . . . . 6 | |
10 | 9 | cneg 10267 | . . . . 5 |
11 | 8, 10, 9 | cif 4086 | . . . 4 |
12 | 6, 5, 11 | cif 4086 | . . 3 |
13 | 2, 3, 12 | cmpt 4729 | . 2 |
14 | 1, 13 | wceq 1483 | 1 sgn |
Colors of variables: wff setvar class |
This definition is referenced by: sgnval 13828 |
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