Description: The absolute value of a real number is either that number or its negative. (Contributed by NM, 27-Feb-2005)
Ref | Expression | ||
---|---|---|---|
Assertion | absor | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 0re | |
|
2 | letric | |
|
3 | 1 2 | mpan | |
4 | absid | |
|
5 | 4 | ex | |
6 | absnid | |
|
7 | 6 | ex | |
8 | 5 7 | orim12d | |
9 | 3 8 | mpd | |