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Theorem tsk1 9465
 Description: One is an element of a nonempty Tarski class. (Contributed by FL, 22-Feb-2011.)
Assertion
Ref Expression
tsk1 ((𝑇 ∈ Tarski ∧ 𝑇 ≠ ∅) → 1𝑜𝑇)

Proof of Theorem tsk1
StepHypRef Expression
1 df1o2 7459 . 2 1𝑜 = {∅}
2 tsk0 9464 . . 3 ((𝑇 ∈ Tarski ∧ 𝑇 ≠ ∅) → ∅ ∈ 𝑇)
3 tsksn 9461 . . 3 ((𝑇 ∈ Tarski ∧ ∅ ∈ 𝑇) → {∅} ∈ 𝑇)
42, 3syldan 486 . 2 ((𝑇 ∈ Tarski ∧ 𝑇 ≠ ∅) → {∅} ∈ 𝑇)
51, 4syl5eqel 2692 1 ((𝑇 ∈ Tarski ∧ 𝑇 ≠ ∅) → 1𝑜𝑇)
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ∧ wa 383   ∈ wcel 1977   ≠ wne 2780  ∅c0 3874  {csn 4125  1𝑜c1o 7440  Tarskictsk 9449 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-9 1986  ax-10 2006  ax-11 2021  ax-12 2034  ax-13 2234  ax-ext 2590  ax-sep 4709  ax-pow 4769 This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  df-3an 1033  df-tru 1478  df-ex 1696  df-nf 1701  df-sb 1868  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-dif 3543  df-un 3545  df-in 3547  df-ss 3554  df-nul 3875  df-if 4037  df-pw 4110  df-sn 4126  df-pr 4128  df-op 4132  df-br 4584  df-suc 5646  df-1o 7447  df-tsk 9450 This theorem is referenced by:  tsk2  9466
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