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Theorem phplem3 8026
 Description: Lemma for Pigeonhole Principle. A natural number is equinumerous to its successor minus any element of the successor. (Contributed by NM, 26-May-1998.)
Hypotheses
Ref Expression
phplem2.1 𝐴 ∈ V
phplem2.2 𝐵 ∈ V
Assertion
Ref Expression
phplem3 ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵}))

Proof of Theorem phplem3
StepHypRef Expression
1 elsuci 5708 . 2 (𝐵 ∈ suc 𝐴 → (𝐵𝐴𝐵 = 𝐴))
2 phplem2.1 . . . 4 𝐴 ∈ V
3 phplem2.2 . . . 4 𝐵 ∈ V
42, 3phplem2 8025 . . 3 ((𝐴 ∈ ω ∧ 𝐵𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵}))
52enref 7874 . . . 4 𝐴𝐴
6 nnord 6965 . . . . . 6 (𝐴 ∈ ω → Ord 𝐴)
7 orddif 5737 . . . . . 6 (Ord 𝐴𝐴 = (suc 𝐴 ∖ {𝐴}))
86, 7syl 17 . . . . 5 (𝐴 ∈ ω → 𝐴 = (suc 𝐴 ∖ {𝐴}))
9 sneq 4135 . . . . . . 7 (𝐴 = 𝐵 → {𝐴} = {𝐵})
109difeq2d 3690 . . . . . 6 (𝐴 = 𝐵 → (suc 𝐴 ∖ {𝐴}) = (suc 𝐴 ∖ {𝐵}))
1110eqcoms 2618 . . . . 5 (𝐵 = 𝐴 → (suc 𝐴 ∖ {𝐴}) = (suc 𝐴 ∖ {𝐵}))
128, 11sylan9eq 2664 . . . 4 ((𝐴 ∈ ω ∧ 𝐵 = 𝐴) → 𝐴 = (suc 𝐴 ∖ {𝐵}))
135, 12syl5breq 4620 . . 3 ((𝐴 ∈ ω ∧ 𝐵 = 𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵}))
144, 13jaodan 822 . 2 ((𝐴 ∈ ω ∧ (𝐵𝐴𝐵 = 𝐴)) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵}))
151, 14sylan2 490 1 ((𝐴 ∈ ω ∧ 𝐵 ∈ suc 𝐴) → 𝐴 ≈ (suc 𝐴 ∖ {𝐵}))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∨ wo 382   ∧ wa 383   = wceq 1475   ∈ wcel 1977  Vcvv 3173   ∖ cdif 3537  {csn 4125   class class class wbr 4583  Ord word 5639  suc csuc 5642  ωcom 6957   ≈ cen 7838 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1713  ax-4 1728  ax-5 1827  ax-6 1875  ax-7 1922  ax-8 1979  ax-9 1986  ax-10 2006  ax-11 2021  ax-12 2034  ax-13 2234  ax-ext 2590  ax-sep 4709  ax-nul 4717  ax-pow 4769  ax-pr 4833  ax-un 6847 This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  df-3or 1032  df-3an 1033  df-tru 1478  df-ex 1696  df-nf 1701  df-sb 1868  df-eu 2462  df-mo 2463  df-clab 2597  df-cleq 2603  df-clel 2606  df-nfc 2740  df-ne 2782  df-ral 2901  df-rex 2902  df-rab 2905  df-v 3175  df-sbc 3403  df-dif 3543  df-un 3545  df-in 3547  df-ss 3554  df-pss 3556  df-nul 3875  df-if 4037  df-pw 4110  df-sn 4126  df-pr 4128  df-tp 4130  df-op 4132  df-uni 4373  df-br 4584  df-opab 4644  df-tr 4681  df-eprel 4949  df-id 4953  df-po 4959  df-so 4960  df-fr 4997  df-we 4999  df-xp 5044  df-rel 5045  df-cnv 5046  df-co 5047  df-dm 5048  df-rn 5049  df-res 5050  df-ima 5051  df-ord 5643  df-on 5644  df-lim 5645  df-suc 5646  df-fun 5806  df-fn 5807  df-f 5808  df-f1 5809  df-fo 5810  df-f1o 5811  df-om 6958  df-en 7842 This theorem is referenced by:  phplem4  8027  php  8029
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