Step |
Hyp |
Ref |
Expression |
1 |
|
0re |
|- 0 e. RR |
2 |
|
ltle |
|- ( ( 0 e. RR /\ A e. RR ) -> ( 0 < A -> 0 <_ A ) ) |
3 |
1 2
|
mpan |
|- ( A e. RR -> ( 0 < A -> 0 <_ A ) ) |
4 |
3
|
imdistani |
|- ( ( A e. RR /\ 0 < A ) -> ( A e. RR /\ 0 <_ A ) ) |
5 |
|
absid |
|- ( ( A e. RR /\ 0 <_ A ) -> ( abs ` A ) = A ) |
6 |
4 5
|
syl |
|- ( ( A e. RR /\ 0 < A ) -> ( abs ` A ) = A ) |
7 |
6
|
eqcomd |
|- ( ( A e. RR /\ 0 < A ) -> A = ( abs ` A ) ) |
8 |
|
id |
|- ( A e. RR -> A e. RR ) |
9 |
|
0red |
|- ( A e. RR -> 0 e. RR ) |
10 |
8 9
|
lenltd |
|- ( A e. RR -> ( A <_ 0 <-> -. 0 < A ) ) |
11 |
10
|
pm5.32i |
|- ( ( A e. RR /\ A <_ 0 ) <-> ( A e. RR /\ -. 0 < A ) ) |
12 |
|
absnid |
|- ( ( A e. RR /\ A <_ 0 ) -> ( abs ` A ) = -u A ) |
13 |
11 12
|
sylbir |
|- ( ( A e. RR /\ -. 0 < A ) -> ( abs ` A ) = -u A ) |
14 |
13
|
eqcomd |
|- ( ( A e. RR /\ -. 0 < A ) -> -u A = ( abs ` A ) ) |
15 |
7 14
|
ifeqda |
|- ( A e. RR -> if ( 0 < A , A , -u A ) = ( abs ` A ) ) |
16 |
15
|
eqcomd |
|- ( A e. RR -> ( abs ` A ) = if ( 0 < A , A , -u A ) ) |