Step |
Hyp |
Ref |
Expression |
1 |
|
sbelx |
|- ( -. ph <-> E. y ( y = x /\ [ y / x ] -. ph ) ) |
2 |
|
sbalex |
|- ( E. y ( y = x /\ [ y / x ] -. ph ) <-> A. y ( y = x -> [ y / x ] -. ph ) ) |
3 |
|
sbn |
|- ( [ y / x ] -. ph <-> -. [ y / x ] ph ) |
4 |
3
|
imbi2i |
|- ( ( y = x -> [ y / x ] -. ph ) <-> ( y = x -> -. [ y / x ] ph ) ) |
5 |
|
con2b |
|- ( ( y = x -> -. [ y / x ] ph ) <-> ( [ y / x ] ph -> -. y = x ) ) |
6 |
|
df-ne |
|- ( y =/= x <-> -. y = x ) |
7 |
6
|
bicomi |
|- ( -. y = x <-> y =/= x ) |
8 |
7
|
imbi2i |
|- ( ( [ y / x ] ph -> -. y = x ) <-> ( [ y / x ] ph -> y =/= x ) ) |
9 |
4 5 8
|
3bitri |
|- ( ( y = x -> [ y / x ] -. ph ) <-> ( [ y / x ] ph -> y =/= x ) ) |
10 |
9
|
albii |
|- ( A. y ( y = x -> [ y / x ] -. ph ) <-> A. y ( [ y / x ] ph -> y =/= x ) ) |
11 |
1 2 10
|
3bitri |
|- ( -. ph <-> A. y ( [ y / x ] ph -> y =/= x ) ) |