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Theorem pltn2lp 18300

Description: The less-than relation has no 2-cycle loops. (pssn2lp 4067 analog.) (Contributed by NM, 2-Dec-2011.)

**Hypotheses**
Ref	Expression
pltnlt.b	⊢ 𝐵 = (Base‘𝐾)
pltnlt.s	⊢ < = (lt‘𝐾)

**Assertion**
Ref	Expression
pltn2lp	⊢ ((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → ¬ (𝑋 < 𝑌 ∧ 𝑌 < 𝑋))

**Proof of Theorem pltn2lp**
Step	Hyp	Ref	Expression
1		pltnlt.b	. . . . 5 ⊢ 𝐵 = (Base‘𝐾)
2		eqid 2729	. . . . 5 ⊢ (le‘𝐾) = (le‘𝐾)
3		pltnlt.s	. . . . 5 ⊢ < = (lt‘𝐾)
4	1, 2, 3	pltnle 18297	. . . 4 ⊢ (((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) ∧ 𝑋 < 𝑌) → ¬ 𝑌(le‘𝐾)𝑋)
5	4	ex 412	. . 3 ⊢ ((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑋 < 𝑌 → ¬ 𝑌(le‘𝐾)𝑋))
6	2, 3	pltle 18292	. . . 4 ⊢ ((𝐾 ∈ Poset ∧ 𝑌 ∈ 𝐵 ∧ 𝑋 ∈ 𝐵) → (𝑌 < 𝑋 → 𝑌(le‘𝐾)𝑋))
7	6	3com23 1126	. . 3 ⊢ ((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑌 < 𝑋 → 𝑌(le‘𝐾)𝑋))
8	5, 7	nsyld 156	. 2 ⊢ ((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → (𝑋 < 𝑌 → ¬ 𝑌 < 𝑋))
9		imnan 399	. 2 ⊢ ((𝑋 < 𝑌 → ¬ 𝑌 < 𝑋) ↔ ¬ (𝑋 < 𝑌 ∧ 𝑌 < 𝑋))
10	8, 9	sylib 218	1 ⊢ ((𝐾 ∈ Poset ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵) → ¬ (𝑋 < 𝑌 ∧ 𝑌 < 𝑋))

Colors of variables: wff setvar class

Syntax hints: ¬ wn 3 → wi 4 ∧ wa 395 ∧ w3a 1086 = wceq 1540 ∈ wcel 2109 class class class wbr 5107 ‘cfv 6511 Basecbs 17179 lecple 17227 Posetcpo 18268 ltcplt 18269

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 2008 ax-8 2111 ax-9 2119 ax-10 2142 ax-11 2158 ax-12 2178 ax-ext 2701 ax-sep 5251 ax-nul 5261 ax-pr 5387

This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3an 1088 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2066 df-mo 2533 df-eu 2562 df-clab 2708 df-cleq 2721 df-clel 2803 df-nfc 2878 df-ne 2926 df-ral 3045 df-rex 3054 df-rab 3406 df-v 3449 df-sbc 3754 df-dif 3917 df-un 3919 df-in 3921 df-ss 3931 df-nul 4297 df-if 4489 df-sn 4590 df-pr 4592 df-op 4596 df-uni 4872 df-br 5108 df-opab 5170 df-mpt 5189 df-id 5533 df-xp 5644 df-rel 5645 df-cnv 5646 df-co 5647 df-dm 5648 df-iota 6464 df-fun 6513 df-fv 6519 df-proset 18255 df-poset 18274 df-plt 18289

This theorem is referenced by: plttr 18301

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