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Theorem 0ntop 20535
 Description: The empty set is not a topology. (Contributed by FL, 1-Jun-2008.)
Assertion
Ref Expression
0ntop ¬ ∅ ∈ Top

Proof of Theorem 0ntop
StepHypRef Expression
1 noel 3878 . 2 ¬ ∅ ∈ ∅
2 0opn 20534 . 2 (∅ ∈ Top → ∅ ∈ ∅)
31, 2mto 187 1 ¬ ∅ ∈ Top
 Colors of variables: wff setvar class Syntax hints:  ¬ wn 3   ∈ wcel 1977  ∅c0 3874  Topctop 20517 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-10 2006  ax-11 2021  ax-12 2034  ax-13 2234  ax-ext 2590  ax-sep 4709 This theorem depends on definitions:  df-bi 196  df-or 384  df-an 385  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-ral 2901  df-rex 2902  df-v 3175  df-dif 3543  df-in 3547  df-ss 3554  df-nul 3875  df-pw 4110  df-sn 4126  df-uni 4373  df-top 20521 This theorem is referenced by:  istps  20551  ordcmp  31616  onint1  31618  kelac1  36651
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