Theorem cniccibl

Description: A continuous function on a closed bounded interval is integrable. (Contributed by Mario Carneiro, 12-Aug-2014)

	Ref	Expression
Assertion	cniccibl	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → 𝐹 ∈ 𝐿1 )

Proof

Step	Hyp	Ref	Expression
1		iccmbl	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( 𝐴 [,] 𝐵 ) ∈ dom vol )
2		cnmbf	⊢ ( ( ( 𝐴 [,] 𝐵 ) ∈ dom vol ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → 𝐹 ∈ MblFn )
3	1 2	stoic3	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → 𝐹 ∈ MblFn )
4		simp3	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) )
5		cncff	⊢ ( 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) → 𝐹 : ( 𝐴 [,] 𝐵 ) ⟶ ℂ )
6		fdm	⊢ ( 𝐹 : ( 𝐴 [,] 𝐵 ) ⟶ ℂ → dom 𝐹 = ( 𝐴 [,] 𝐵 ) )
7	4 5 6	3syl	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → dom 𝐹 = ( 𝐴 [,] 𝐵 ) )
8	7	fveq2d	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ( vol ‘ dom 𝐹 ) = ( vol ‘ ( 𝐴 [,] 𝐵 ) ) )
9		iccvolcl	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ) → ( vol ‘ ( 𝐴 [,] 𝐵 ) ) ∈ ℝ )
10	9	3adant3	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ( vol ‘ ( 𝐴 [,] 𝐵 ) ) ∈ ℝ )
11	8 10	eqeltrd	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ( vol ‘ dom 𝐹 ) ∈ ℝ )
12		cniccbdd	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ∃ 𝑥 ∈ ℝ ∀ 𝑦 ∈ ( 𝐴 [,] 𝐵 ) ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 )
13	7	raleqdv	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ( ∀ 𝑦 ∈ dom 𝐹 ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 ↔ ∀ 𝑦 ∈ ( 𝐴 [,] 𝐵 ) ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 ) )
14	13	rexbidv	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ( ∃ 𝑥 ∈ ℝ ∀ 𝑦 ∈ dom 𝐹 ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 ↔ ∃ 𝑥 ∈ ℝ ∀ 𝑦 ∈ ( 𝐴 [,] 𝐵 ) ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 ) )
15	12 14	mpbird	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → ∃ 𝑥 ∈ ℝ ∀ 𝑦 ∈ dom 𝐹 ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 )
16		bddibl	⊢ ( ( 𝐹 ∈ MblFn ∧ ( vol ‘ dom 𝐹 ) ∈ ℝ ∧ ∃ 𝑥 ∈ ℝ ∀ 𝑦 ∈ dom 𝐹 ( abs ‘ ( 𝐹 ‘ 𝑦 ) ) ≤ 𝑥 ) → 𝐹 ∈ 𝐿1 )
17	3 11 15 16	syl3anc	⊢ ( ( 𝐴 ∈ ℝ ∧ 𝐵 ∈ ℝ ∧ 𝐹 ∈ ( ( 𝐴 [,] 𝐵 ) –cn→ ℂ ) ) → 𝐹 ∈ 𝐿1 )