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Related theorems Unicode version |
| Description: Negate both sides of a logical equivalence. |
| Ref | Expression |
|---|---|
| bi.a |
|
| Ref | Expression |
|---|---|
| notbii |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | bi.a |
. . . 4
| |
| 2 | 1 | biimpri 230 |
. . 3
|
| 3 | 2 | con3i 149 |
. 2
|
| 4 | 1 | biimpi 224 |
. . 3
|
| 5 | 4 | con3i 149 |
. 2
|
| 6 | 3, 5 | impbii 223 |
1
|