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Mirrors > Home > ILE Home > Th. List > difeq2 | GIF version |
Description: Equality theorem for class difference. (Contributed by NM, 10-Feb-1997.) (Proof shortened by Andrew Salmon, 26-Jun-2011.) |
Ref | Expression |
---|---|
difeq2 | ⊢ (𝐴 = 𝐵 → (𝐶 ∖ 𝐴) = (𝐶 ∖ 𝐵)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eleq2 2228 | . . . 4 ⊢ (𝐴 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵)) | |
2 | 1 | notbid 657 | . . 3 ⊢ (𝐴 = 𝐵 → (¬ 𝑥 ∈ 𝐴 ↔ ¬ 𝑥 ∈ 𝐵)) |
3 | 2 | rabbidv 2710 | . 2 ⊢ (𝐴 = 𝐵 → {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵}) |
4 | dfdif2 3119 | . 2 ⊢ (𝐶 ∖ 𝐴) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} | |
5 | dfdif2 3119 | . 2 ⊢ (𝐶 ∖ 𝐵) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵} | |
6 | 3, 4, 5 | 3eqtr4g 2222 | 1 ⊢ (𝐴 = 𝐵 → (𝐶 ∖ 𝐴) = (𝐶 ∖ 𝐵)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 = wceq 1342 ∈ wcel 2135 {crab 2446 ∖ cdif 3108 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 604 ax-in2 605 ax-5 1434 ax-7 1435 ax-gen 1436 ax-ie1 1480 ax-ie2 1481 ax-8 1491 ax-11 1493 ax-4 1497 ax-17 1513 ax-i9 1517 ax-ial 1521 ax-i5r 1522 ax-ext 2146 |
This theorem depends on definitions: df-bi 116 df-tru 1345 df-nf 1448 df-sb 1750 df-clab 2151 df-cleq 2157 df-clel 2160 df-ral 2447 df-rab 2451 df-dif 3113 |
This theorem is referenced by: difeq12 3230 difeq2i 3232 difeq2d 3235 disjdif2 3482 ssdifeq0 3486 2oconcl 6398 diffitest 6844 diffifi 6851 undifdc 6880 sbthlem2 6914 isbth 6923 difinfinf 7057 ismkvnex 7110 iscld 12644 |
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