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Theorem cnconst 21179
 Description: A constant function is continuous. (Contributed by FL, 15-Jan-2007.) (Proof shortened by Mario Carneiro, 19-Mar-2015.)
Assertion
Ref Expression
cnconst (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ (𝐵𝑌𝐹:𝑋⟶{𝐵})) → 𝐹 ∈ (𝐽 Cn 𝐾))

Proof of Theorem cnconst
StepHypRef Expression
1 fconst2g 6552 . . . 4 (𝐵𝑌 → (𝐹:𝑋⟶{𝐵} ↔ 𝐹 = (𝑋 × {𝐵})))
21adantl 473 . . 3 (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ 𝐵𝑌) → (𝐹:𝑋⟶{𝐵} ↔ 𝐹 = (𝑋 × {𝐵})))
3 cnconst2 21178 . . . . 5 ((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌) ∧ 𝐵𝑌) → (𝑋 × {𝐵}) ∈ (𝐽 Cn 𝐾))
433expa 1111 . . . 4 (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ 𝐵𝑌) → (𝑋 × {𝐵}) ∈ (𝐽 Cn 𝐾))
5 eleq1 2759 . . . 4 (𝐹 = (𝑋 × {𝐵}) → (𝐹 ∈ (𝐽 Cn 𝐾) ↔ (𝑋 × {𝐵}) ∈ (𝐽 Cn 𝐾)))
64, 5syl5ibrcom 237 . . 3 (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ 𝐵𝑌) → (𝐹 = (𝑋 × {𝐵}) → 𝐹 ∈ (𝐽 Cn 𝐾)))
72, 6sylbid 230 . 2 (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ 𝐵𝑌) → (𝐹:𝑋⟶{𝐵} → 𝐹 ∈ (𝐽 Cn 𝐾)))
87impr 650 1 (((𝐽 ∈ (TopOn‘𝑋) ∧ 𝐾 ∈ (TopOn‘𝑌)) ∧ (𝐵𝑌𝐹:𝑋⟶{𝐵})) → 𝐹 ∈ (𝐽 Cn 𝐾))
 Colors of variables: wff setvar class Syntax hints:   → wi 4   ↔ wb 196   ∧ wa 383   = wceq 1564   ∈ wcel 2071  {csn 4253   × cxp 5184  ⟶wf 5965  ‘cfv 5969  (class class class)co 6733  TopOnctopon 20806   Cn ccn 21119 This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1803  ax-4 1818  ax-5 1920  ax-6 1986  ax-7 2022  ax-8 2073  ax-9 2080  ax-10 2100  ax-11 2115  ax-12 2128  ax-13 2323  ax-ext 2672  ax-sep 4857  ax-nul 4865  ax-pow 4916  ax-pr 4979  ax-un 7034 This theorem depends on definitions:  df-bi 197  df-or 384  df-an 385  df-3an 1074  df-tru 1567  df-ex 1786  df-nf 1791  df-sb 1979  df-eu 2543  df-mo 2544  df-clab 2679  df-cleq 2685  df-clel 2688  df-nfc 2823  df-ne 2865  df-ral 2987  df-rex 2988  df-rab 2991  df-v 3274  df-sbc 3510  df-csb 3608  df-dif 3651  df-un 3653  df-in 3655  df-ss 3662  df-nul 3992  df-if 4163  df-pw 4236  df-sn 4254  df-pr 4256  df-op 4260  df-uni 4513  df-iun 4598  df-br 4729  df-opab 4789  df-mpt 4806  df-id 5096  df-xp 5192  df-rel 5193  df-cnv 5194  df-co 5195  df-dm 5196  df-rn 5197  df-res 5198  df-ima 5199  df-iota 5932  df-fun 5971  df-fn 5972  df-f 5973  df-fv 5977  df-ov 6736  df-oprab 6737  df-mpt2 6738  df-1st 7253  df-2nd 7254  df-map 7944  df-topgen 16195  df-top 20790  df-topon 20807  df-cn 21122  df-cnp 21123 This theorem is referenced by:  xrge0mulc1cn  30185  cxpcncf2  40501
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