Metamath Proof Explorer


Theorem cncfshiftioo

Description: A periodic continuous function stays continuous if the domain is an open interval that is shifted a period. (Contributed by Glauco Siliprandi, 11-Dec-2019)

Ref Expression
Hypotheses cncfshiftioo.a ( 𝜑𝐴 ∈ ℝ )
cncfshiftioo.b ( 𝜑𝐵 ∈ ℝ )
cncfshiftioo.c 𝐶 = ( 𝐴 (,) 𝐵 )
cncfshiftioo.t ( 𝜑𝑇 ∈ ℝ )
cncfshiftioo.d 𝐷 = ( ( 𝐴 + 𝑇 ) (,) ( 𝐵 + 𝑇 ) )
cncfshiftioo.f ( 𝜑𝐹 ∈ ( 𝐶cn→ ℂ ) )
cncfshiftioo.g 𝐺 = ( 𝑥𝐷 ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) )
Assertion cncfshiftioo ( 𝜑𝐺 ∈ ( 𝐷cn→ ℂ ) )

Proof

Step Hyp Ref Expression
1 cncfshiftioo.a ( 𝜑𝐴 ∈ ℝ )
2 cncfshiftioo.b ( 𝜑𝐵 ∈ ℝ )
3 cncfshiftioo.c 𝐶 = ( 𝐴 (,) 𝐵 )
4 cncfshiftioo.t ( 𝜑𝑇 ∈ ℝ )
5 cncfshiftioo.d 𝐷 = ( ( 𝐴 + 𝑇 ) (,) ( 𝐵 + 𝑇 ) )
6 cncfshiftioo.f ( 𝜑𝐹 ∈ ( 𝐶cn→ ℂ ) )
7 cncfshiftioo.g 𝐺 = ( 𝑥𝐷 ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) )
8 ioosscn ( 𝐴 (,) 𝐵 ) ⊆ ℂ
9 8 a1i ( 𝜑 → ( 𝐴 (,) 𝐵 ) ⊆ ℂ )
10 4 recnd ( 𝜑𝑇 ∈ ℂ )
11 eqeq1 ( 𝑤 = 𝑥 → ( 𝑤 = ( 𝑧 + 𝑇 ) ↔ 𝑥 = ( 𝑧 + 𝑇 ) ) )
12 11 rexbidv ( 𝑤 = 𝑥 → ( ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) ↔ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑥 = ( 𝑧 + 𝑇 ) ) )
13 oveq1 ( 𝑧 = 𝑦 → ( 𝑧 + 𝑇 ) = ( 𝑦 + 𝑇 ) )
14 13 eqeq2d ( 𝑧 = 𝑦 → ( 𝑥 = ( 𝑧 + 𝑇 ) ↔ 𝑥 = ( 𝑦 + 𝑇 ) ) )
15 14 cbvrexvw ( ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑥 = ( 𝑧 + 𝑇 ) ↔ ∃ 𝑦 ∈ ( 𝐴 (,) 𝐵 ) 𝑥 = ( 𝑦 + 𝑇 ) )
16 12 15 bitrdi ( 𝑤 = 𝑥 → ( ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) ↔ ∃ 𝑦 ∈ ( 𝐴 (,) 𝐵 ) 𝑥 = ( 𝑦 + 𝑇 ) ) )
17 16 cbvrabv { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } = { 𝑥 ∈ ℂ ∣ ∃ 𝑦 ∈ ( 𝐴 (,) 𝐵 ) 𝑥 = ( 𝑦 + 𝑇 ) }
18 3 oveq1i ( 𝐶cn→ ℂ ) = ( ( 𝐴 (,) 𝐵 ) –cn→ ℂ )
19 6 18 eleqtrdi ( 𝜑𝐹 ∈ ( ( 𝐴 (,) 𝐵 ) –cn→ ℂ ) )
20 eqid ( 𝑥 ∈ { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) ) = ( 𝑥 ∈ { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) )
21 9 10 17 19 20 cncfshift ( 𝜑 → ( 𝑥 ∈ { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) ) ∈ ( { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } –cn→ ℂ ) )
22 1 2 4 iooshift ( 𝜑 → ( ( 𝐴 + 𝑇 ) (,) ( 𝐵 + 𝑇 ) ) = { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } )
23 5 22 syl5eq ( 𝜑𝐷 = { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } )
24 23 mpteq1d ( 𝜑 → ( 𝑥𝐷 ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) ) = ( 𝑥 ∈ { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) ) )
25 7 24 syl5eq ( 𝜑𝐺 = ( 𝑥 ∈ { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } ↦ ( 𝐹 ‘ ( 𝑥𝑇 ) ) ) )
26 23 oveq1d ( 𝜑 → ( 𝐷cn→ ℂ ) = ( { 𝑤 ∈ ℂ ∣ ∃ 𝑧 ∈ ( 𝐴 (,) 𝐵 ) 𝑤 = ( 𝑧 + 𝑇 ) } –cn→ ℂ ) )
27 21 25 26 3eltr4d ( 𝜑𝐺 ∈ ( 𝐷cn→ ℂ ) )