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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 2101 | . . . 4 ⊢ (𝐴 = 𝐵 → (𝑥 ∈ 𝐴 ↔ 𝑥 ∈ 𝐵)) | |
2 | 1 | notbid 592 | . . 3 ⊢ (𝐴 = 𝐵 → (¬ 𝑥 ∈ 𝐴 ↔ ¬ 𝑥 ∈ 𝐵)) |
3 | 2 | rabbidv 2549 | . 2 ⊢ (𝐴 = 𝐵 → {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵}) |
4 | dfdif2 2926 | . 2 ⊢ (𝐶 ∖ 𝐴) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐴} | |
5 | dfdif2 2926 | . 2 ⊢ (𝐶 ∖ 𝐵) = {𝑥 ∈ 𝐶 ∣ ¬ 𝑥 ∈ 𝐵} | |
6 | 3, 4, 5 | 3eqtr4g 2097 | 1 ⊢ (𝐴 = 𝐵 → (𝐶 ∖ 𝐴) = (𝐶 ∖ 𝐵)) |
Colors of variables: wff set class |
Syntax hints: ¬ wn 3 → wi 4 = wceq 1243 ∈ wcel 1393 {crab 2310 ∖ cdif 2914 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 99 ax-ia2 100 ax-ia3 101 ax-in1 544 ax-in2 545 ax-5 1336 ax-7 1337 ax-gen 1338 ax-ie1 1382 ax-ie2 1383 ax-8 1395 ax-11 1397 ax-4 1400 ax-17 1419 ax-i9 1423 ax-ial 1427 ax-i5r 1428 ax-ext 2022 |
This theorem depends on definitions: df-bi 110 df-tru 1246 df-nf 1350 df-sb 1646 df-clab 2027 df-cleq 2033 df-clel 2036 df-ral 2311 df-rab 2315 df-dif 2920 |
This theorem is referenced by: difeq12 3057 difeq2i 3059 difeq2d 3062 ssdifeq0 3305 2oconcl 6022 diffitest 6344 diffifi 6351 |
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