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Mirrors > Home > ILE Home > Th. List > ifiddc | GIF version |
Description: Identical true and false arguments in the conditional operator. (Contributed by NM, 18-Apr-2005.) |
Ref | Expression |
---|---|
ifiddc | ⊢ (DECID 𝜑 → if(𝜑, 𝐴, 𝐴) = 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | exmiddc 785 | . 2 ⊢ (DECID 𝜑 → (𝜑 ∨ ¬ 𝜑)) | |
2 | iftrue 3418 | . . 3 ⊢ (𝜑 → if(𝜑, 𝐴, 𝐴) = 𝐴) | |
3 | iffalse 3421 | . . 3 ⊢ (¬ 𝜑 → if(𝜑, 𝐴, 𝐴) = 𝐴) | |
4 | 2, 3 | jaoi 674 | . 2 ⊢ ((𝜑 ∨ ¬ 𝜑) → if(𝜑, 𝐴, 𝐴) = 𝐴) |
5 | 1, 4 | syl 14 | 1 ⊢ (DECID 𝜑 → if(𝜑, 𝐴, 𝐴) = 𝐴) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 ∨ wo 667 DECID wdc 783 = wceq 1296 ifcif 3413 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in2 583 ax-io 668 ax-5 1388 ax-7 1389 ax-gen 1390 ax-ie1 1434 ax-ie2 1435 ax-8 1447 ax-11 1449 ax-4 1452 ax-17 1471 ax-i9 1475 ax-ial 1479 ax-i5r 1480 ax-ext 2077 |
This theorem depends on definitions: df-bi 116 df-dc 784 df-nf 1402 df-sb 1700 df-clab 2082 df-cleq 2088 df-clel 2091 df-if 3414 |
This theorem is referenced by: xaddpnf1 9412 xaddmnf1 9414 isumz 10932 |
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