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Mirrors > Home > ILE Home > Th. List > sstr2 | GIF version |
Description: Transitivity of subclasses. Exercise 5 of [TakeutiZaring] p. 17. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 14-Jun-2011.) |
Ref | Expression |
---|---|
sstr2 | ⊢ (𝐴 ⊆ 𝐵 → (𝐵 ⊆ 𝐶 → 𝐴 ⊆ 𝐶)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ssel 3096 | . . . 4 ⊢ (𝐴 ⊆ 𝐵 → (𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐵)) | |
2 | 1 | imim1d 75 | . . 3 ⊢ (𝐴 ⊆ 𝐵 → ((𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐶) → (𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐶))) |
3 | 2 | alimdv 1852 | . 2 ⊢ (𝐴 ⊆ 𝐵 → (∀𝑥(𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐶) → ∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐶))) |
4 | dfss2 3091 | . 2 ⊢ (𝐵 ⊆ 𝐶 ↔ ∀𝑥(𝑥 ∈ 𝐵 → 𝑥 ∈ 𝐶)) | |
5 | dfss2 3091 | . 2 ⊢ (𝐴 ⊆ 𝐶 ↔ ∀𝑥(𝑥 ∈ 𝐴 → 𝑥 ∈ 𝐶)) | |
6 | 3, 4, 5 | 3imtr4g 204 | 1 ⊢ (𝐴 ⊆ 𝐵 → (𝐵 ⊆ 𝐶 → 𝐴 ⊆ 𝐶)) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∀wal 1330 ∈ wcel 1481 ⊆ wss 3076 |
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-5 1424 ax-7 1425 ax-gen 1426 ax-ie1 1470 ax-ie2 1471 ax-8 1483 ax-11 1485 ax-4 1488 ax-17 1507 ax-i9 1511 ax-ial 1515 ax-i5r 1516 ax-ext 2122 |
This theorem depends on definitions: df-bi 116 df-nf 1438 df-sb 1737 df-clab 2127 df-cleq 2133 df-clel 2136 df-in 3082 df-ss 3089 |
This theorem is referenced by: sstr 3110 sstri 3111 sseq1 3125 sseq2 3126 ssun3 3246 ssun4 3247 ssinss1 3310 ssdisj 3424 triun 4047 trintssm 4050 sspwb 4146 exss 4157 relss 4634 funss 5150 funimass2 5209 fss 5292 fiintim 6825 sbthlem2 6854 sbthlemi3 6855 sbthlemi6 6858 tgss 12271 tgcl 12272 tgss3 12286 clsss 12326 neiss 12358 ssnei2 12365 cnpnei 12427 cnptopco 12430 cnptoprest 12447 txcnp 12479 neibl 12699 metcnp3 12719 bj-nntrans 13320 |
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