Theorem iimulcn

Description: Multiplication is a continuous function on the unit interval. (Contributed by Mario Carneiro, 8-Jun-2014)

	Ref	Expression
Assertion	iimulcn	⊢ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn II )

Proof

Step	Hyp	Ref	Expression
1		eqid	⊢ ( TopOpen ‘ ℂfld ) = ( TopOpen ‘ ℂfld )
2	1	dfii3	⊢ II = ( ( TopOpen ‘ ℂfld ) ↾t ( 0 [,] 1 ) )
3	1	cnfldtopon	⊢ ( TopOpen ‘ ℂfld ) ∈ ( TopOn ‘ ℂ )
4	3	a1i	⊢ ( ⊤ → ( TopOpen ‘ ℂfld ) ∈ ( TopOn ‘ ℂ ) )
5		unitssre	⊢ ( 0 [,] 1 ) ⊆ ℝ
6		ax-resscn	⊢ ℝ ⊆ ℂ
7	5 6	sstri	⊢ ( 0 [,] 1 ) ⊆ ℂ
8	7	a1i	⊢ ( ⊤ → ( 0 [,] 1 ) ⊆ ℂ )
9		ax-mulf	⊢ · : ( ℂ × ℂ ) ⟶ ℂ
10		ffn	⊢ ( · : ( ℂ × ℂ ) ⟶ ℂ → · Fn ( ℂ × ℂ ) )
11	9 10	ax-mp	⊢ · Fn ( ℂ × ℂ )
12		fnov	⊢ ( · Fn ( ℂ × ℂ ) ↔ · = ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) )
13	11 12	mpbi	⊢ · = ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) )
14	1	mulcn	⊢ · ∈ ( ( ( TopOpen ‘ ℂfld ) ×t ( TopOpen ‘ ℂfld ) ) Cn ( TopOpen ‘ ℂfld ) )
15	13 14	eqeltrri	⊢ ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( ( TopOpen ‘ ℂfld ) ×t ( TopOpen ‘ ℂfld ) ) Cn ( TopOpen ‘ ℂfld ) )
16	15	a1i	⊢ ( ⊤ → ( 𝑥 ∈ ℂ , 𝑦 ∈ ℂ ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( ( TopOpen ‘ ℂfld ) ×t ( TopOpen ‘ ℂfld ) ) Cn ( TopOpen ‘ ℂfld ) ) )
17	2 4 8 2 4 8 16	cnmpt2res	⊢ ( ⊤ → ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( TopOpen ‘ ℂfld ) ) )
18	17	mptru	⊢ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( TopOpen ‘ ℂfld ) )
19		iimulcl	⊢ ( ( 𝑥 ∈ ( 0 [,] 1 ) ∧ 𝑦 ∈ ( 0 [,] 1 ) ) → ( 𝑥 · 𝑦 ) ∈ ( 0 [,] 1 ) )
20	19	rgen2	⊢ ∀ 𝑥 ∈ ( 0 [,] 1 ) ∀ 𝑦 ∈ ( 0 [,] 1 ) ( 𝑥 · 𝑦 ) ∈ ( 0 [,] 1 )
21		eqid	⊢ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) = ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) )
22	21	fmpo	⊢ ( ∀ 𝑥 ∈ ( 0 [,] 1 ) ∀ 𝑦 ∈ ( 0 [,] 1 ) ( 𝑥 · 𝑦 ) ∈ ( 0 [,] 1 ) ↔ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) : ( ( 0 [,] 1 ) × ( 0 [,] 1 ) ) ⟶ ( 0 [,] 1 ) )
23		frn	⊢ ( ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) : ( ( 0 [,] 1 ) × ( 0 [,] 1 ) ) ⟶ ( 0 [,] 1 ) → ran ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ⊆ ( 0 [,] 1 ) )
24	22 23	sylbi	⊢ ( ∀ 𝑥 ∈ ( 0 [,] 1 ) ∀ 𝑦 ∈ ( 0 [,] 1 ) ( 𝑥 · 𝑦 ) ∈ ( 0 [,] 1 ) → ran ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ⊆ ( 0 [,] 1 ) )
25	20 24	ax-mp	⊢ ran ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ⊆ ( 0 [,] 1 )
26		cnrest2	⊢ ( ( ( TopOpen ‘ ℂfld ) ∈ ( TopOn ‘ ℂ ) ∧ ran ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ⊆ ( 0 [,] 1 ) ∧ ( 0 [,] 1 ) ⊆ ℂ ) → ( ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( TopOpen ‘ ℂfld ) ) ↔ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( ( TopOpen ‘ ℂfld ) ↾t ( 0 [,] 1 ) ) ) ) )
27	3 25 7 26	mp3an	⊢ ( ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( TopOpen ‘ ℂfld ) ) ↔ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( ( TopOpen ‘ ℂfld ) ↾t ( 0 [,] 1 ) ) ) )
28	18 27	mpbi	⊢ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn ( ( TopOpen ‘ ℂfld ) ↾t ( 0 [,] 1 ) ) )
29	2	oveq2i	⊢ ( ( II ×t II ) Cn II ) = ( ( II ×t II ) Cn ( ( TopOpen ‘ ℂfld ) ↾t ( 0 [,] 1 ) ) )
30	28 29	eleqtrri	⊢ ( 𝑥 ∈ ( 0 [,] 1 ) , 𝑦 ∈ ( 0 [,] 1 ) ↦ ( 𝑥 · 𝑦 ) ) ∈ ( ( II ×t II ) Cn II )