Description: One direction of dffrege115 . Proposition 116 of Frege1879 p. 77. (Contributed by RP, 8-Jul-2020) (Proof modification is discouraged.)
Ref | Expression | ||
---|---|---|---|
Hypothesis | frege116.x | |
|
Assertion | frege116 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frege116.x | |
|
2 | dffrege115 | |
|
3 | 1 | frege68c | |
4 | sbcal | |
|
5 | sbcimg | |
|
6 | 1 5 | ax-mp | |
7 | sbcbr2g | |
|
8 | 1 7 | ax-mp | |
9 | csbvarg | |
|
10 | 1 9 | ax-mp | |
11 | 10 | breq2i | |
12 | 8 11 | bitri | |
13 | sbcal | |
|
14 | sbcimg | |
|
15 | 1 14 | ax-mp | |
16 | sbcg | |
|
17 | 1 16 | ax-mp | |
18 | sbceq2g | |
|
19 | 1 18 | ax-mp | |
20 | 10 | eqeq2i | |
21 | 19 20 | bitri | |
22 | 17 21 | imbi12i | |
23 | 15 22 | bitri | |
24 | 23 | albii | |
25 | 13 24 | bitri | |
26 | 12 25 | imbi12i | |
27 | 6 26 | bitri | |
28 | 27 | albii | |
29 | 4 28 | bitri | |
30 | 3 29 | imbitrdi | |
31 | 2 30 | ax-mp | |