Metamath Proof Explorer


Theorem preimaiocmnf

Description: Preimage of a right-closed interval, unbounded below. (Contributed by Glauco Siliprandi, 23-Oct-2021)

Ref Expression
Hypotheses preimaiocmnf.1 ( 𝜑𝐹 : 𝐴 ⟶ ℝ )
preimaiocmnf.2 ( 𝜑𝐵 ∈ ℝ* )
Assertion preimaiocmnf ( 𝜑 → ( 𝐹 “ ( -∞ (,] 𝐵 ) ) = { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ≤ 𝐵 } )

Proof

Step Hyp Ref Expression
1 preimaiocmnf.1 ( 𝜑𝐹 : 𝐴 ⟶ ℝ )
2 preimaiocmnf.2 ( 𝜑𝐵 ∈ ℝ* )
3 1 ffnd ( 𝜑𝐹 Fn 𝐴 )
4 fncnvima2 ( 𝐹 Fn 𝐴 → ( 𝐹 “ ( -∞ (,] 𝐵 ) ) = { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) } )
5 3 4 syl ( 𝜑 → ( 𝐹 “ ( -∞ (,] 𝐵 ) ) = { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) } )
6 mnfxr -∞ ∈ ℝ*
7 6 a1i ( ( 𝜑 ∧ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ) → -∞ ∈ ℝ* )
8 2 adantr ( ( 𝜑 ∧ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ) → 𝐵 ∈ ℝ* )
9 simpr ( ( 𝜑 ∧ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ) → ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) )
10 7 8 9 iocleubd ( ( 𝜑 ∧ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ) → ( 𝐹𝑥 ) ≤ 𝐵 )
11 10 ex ( 𝜑 → ( ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) → ( 𝐹𝑥 ) ≤ 𝐵 ) )
12 11 adantr ( ( 𝜑𝑥𝐴 ) → ( ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) → ( 𝐹𝑥 ) ≤ 𝐵 ) )
13 6 a1i ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → -∞ ∈ ℝ* )
14 2 adantr ( ( 𝜑 ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → 𝐵 ∈ ℝ* )
15 14 adantlr ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → 𝐵 ∈ ℝ* )
16 1 ffvelrnda ( ( 𝜑𝑥𝐴 ) → ( 𝐹𝑥 ) ∈ ℝ )
17 16 rexrd ( ( 𝜑𝑥𝐴 ) → ( 𝐹𝑥 ) ∈ ℝ* )
18 17 adantr ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → ( 𝐹𝑥 ) ∈ ℝ* )
19 16 mnfltd ( ( 𝜑𝑥𝐴 ) → -∞ < ( 𝐹𝑥 ) )
20 19 adantr ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → -∞ < ( 𝐹𝑥 ) )
21 simpr ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → ( 𝐹𝑥 ) ≤ 𝐵 )
22 13 15 18 20 21 eliocd ( ( ( 𝜑𝑥𝐴 ) ∧ ( 𝐹𝑥 ) ≤ 𝐵 ) → ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) )
23 22 ex ( ( 𝜑𝑥𝐴 ) → ( ( 𝐹𝑥 ) ≤ 𝐵 → ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ) )
24 12 23 impbid ( ( 𝜑𝑥𝐴 ) → ( ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) ↔ ( 𝐹𝑥 ) ≤ 𝐵 ) )
25 24 rabbidva ( 𝜑 → { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ∈ ( -∞ (,] 𝐵 ) } = { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ≤ 𝐵 } )
26 5 25 eqtrd ( 𝜑 → ( 𝐹 “ ( -∞ (,] 𝐵 ) ) = { 𝑥𝐴 ∣ ( 𝐹𝑥 ) ≤ 𝐵 } )