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Theorem nosgnn0i 27030
Description: If 𝑋 is a surreal sign, then it is not null. (Contributed by Scott Fenton, 3-Aug-2011.)
Hypothesis
Ref Expression
nosgnn0i.1 𝑋 ∈ {1o, 2o}
Assertion
Ref Expression
nosgnn0i ∅ ≠ 𝑋

Proof of Theorem nosgnn0i
StepHypRef Expression
1 nosgnn0 27029 . . 3 ¬ ∅ ∈ {1o, 2o}
2 nosgnn0i.1 . . . 4 𝑋 ∈ {1o, 2o}
3 eleq1 2822 . . . 4 (∅ = 𝑋 → (∅ ∈ {1o, 2o} ↔ 𝑋 ∈ {1o, 2o}))
42, 3mpbiri 258 . . 3 (∅ = 𝑋 → ∅ ∈ {1o, 2o})
51, 4mto 196 . 2 ¬ ∅ = 𝑋
65neir 2943 1 ∅ ≠ 𝑋
Colors of variables: wff setvar class
Syntax hints:   = wceq 1542  wcel 2107  wne 2940  c0 4286  {cpr 4592  1oc1o 8409  2oc2o 8410
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-ext 2704  ax-nul 5267
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-tru 1545  df-fal 1555  df-ex 1783  df-sb 2069  df-clab 2711  df-cleq 2725  df-clel 2811  df-ne 2941  df-v 3449  df-dif 3917  df-un 3919  df-nul 4287  df-sn 4591  df-pr 4593  df-suc 6327  df-1o 8416  df-2o 8417
This theorem is referenced by:  sltres  27033  noextenddif  27039  nolesgn2ores  27043  nosepnelem  27050  nosepdmlem  27054  nolt02o  27066  nosupbnd1lem3  27081  nosupbnd1lem5  27083  nosupbnd2lem1  27086
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