Step |
Hyp |
Ref |
Expression |
1 |
|
idn1 |
|
2 |
|
eqsbc3 |
|
3 |
1 2
|
e1a |
|
4 |
|
eqcom |
|
5 |
4
|
sbcbii |
|
6 |
5
|
a1i |
|
7 |
1 6
|
e1a |
|
8 |
|
idn2 |
|
9 |
|
biimp |
|
10 |
7 8 9
|
e12 |
|
11 |
|
biimp |
|
12 |
3 10 11
|
e12 |
|
13 |
|
eqcom |
|
14 |
12 13
|
e2bi |
|
15 |
14
|
in2 |
|
16 |
|
idn2 |
|
17 |
16 13
|
e2bir |
|
18 |
|
biimpr |
|
19 |
3 17 18
|
e12 |
|
20 |
|
biimpr |
|
21 |
7 19 20
|
e12 |
|
22 |
21
|
in2 |
|
23 |
|
impbi |
|
24 |
15 22 23
|
e11 |
|
25 |
24
|
in1 |
|