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Mirrors > Home > NFE Home > Th. List > nic-idbl | Unicode version |
Description: Double the terms. Since doubling is the same as negation, this can be viewed as a contraposition inference. (Contributed by Jeff Hoffman, 17-Nov-2007.) (Proof modification is discouraged.) (New usage is discouraged.) |
Ref | Expression |
---|---|
nic-idbl.1 |
Ref | Expression |
---|---|
nic-idbl |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nic-idbl.1 | . . 3 | |
2 | 1 | nic-imp 1440 | . 2 |
3 | 1 | nic-imp 1440 | . 2 |
4 | 2, 3 | nic-ich 1450 | 1 |
Colors of variables: wff setvar class |
Syntax hints: wnan 1287 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 |
This theorem depends on definitions: df-bi 177 df-an 360 df-nan 1288 |
This theorem is referenced by: nic-luk1 1456 |
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