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| Mirrors > Home > MPE Home > Th. List > psssstr | Structured version Visualization version GIF version | ||
| Description: Transitive law for subclass and proper subclass. (Contributed by NM, 3-Apr-1996.) |
| Ref | Expression |
|---|---|
| psssstr | ⊢ ((𝐴 ⊊ 𝐵 ∧ 𝐵 ⊆ 𝐶) → 𝐴 ⊊ 𝐶) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sspss 4102 | . 2 ⊢ (𝐵 ⊆ 𝐶 ↔ (𝐵 ⊊ 𝐶 ∨ 𝐵 = 𝐶)) | |
| 2 | psstr 4107 | . . . . 5 ⊢ ((𝐴 ⊊ 𝐵 ∧ 𝐵 ⊊ 𝐶) → 𝐴 ⊊ 𝐶) | |
| 3 | 2 | ex 412 | . . . 4 ⊢ (𝐴 ⊊ 𝐵 → (𝐵 ⊊ 𝐶 → 𝐴 ⊊ 𝐶)) |
| 4 | psseq2 4091 | . . . . 5 ⊢ (𝐵 = 𝐶 → (𝐴 ⊊ 𝐵 ↔ 𝐴 ⊊ 𝐶)) | |
| 5 | 4 | biimpcd 249 | . . . 4 ⊢ (𝐴 ⊊ 𝐵 → (𝐵 = 𝐶 → 𝐴 ⊊ 𝐶)) |
| 6 | 3, 5 | jaod 860 | . . 3 ⊢ (𝐴 ⊊ 𝐵 → ((𝐵 ⊊ 𝐶 ∨ 𝐵 = 𝐶) → 𝐴 ⊊ 𝐶)) |
| 7 | 6 | imp 406 | . 2 ⊢ ((𝐴 ⊊ 𝐵 ∧ (𝐵 ⊊ 𝐶 ∨ 𝐵 = 𝐶)) → 𝐴 ⊊ 𝐶) |
| 8 | 1, 7 | sylan2b 594 | 1 ⊢ ((𝐴 ⊊ 𝐵 ∧ 𝐵 ⊆ 𝐶) → 𝐴 ⊊ 𝐶) |
| Colors of variables: wff setvar class |
| Syntax hints: → wi 4 ∧ wa 395 ∨ wo 848 = wceq 1540 ⊆ wss 3951 ⊊ wpss 3952 |
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1967 ax-7 2007 ax-9 2118 ax-ext 2708 |
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-ex 1780 df-cleq 2729 df-ne 2941 df-ss 3968 df-pss 3971 |
| This theorem is referenced by: psssstrd 4112 suplem1pr 11092 atexch 32400 bj-2upln0 37024 bj-2upln1upl 37025 |
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