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Metamath Proof Explorer

Theorem mgcf1

Description: The lower adjoint F of a Galois connection is a function. (Contributed by Thierry Arnoux, 24-Apr-2024)

Ref Expression
Hypotheses mgcoval.1 ⊢ 𝐴 = ( Base ‘ 𝑉 )
mgcoval.2 ⊢ 𝐵 = ( Base ‘ 𝑊 )
mgcoval.3 ⊢ ≤ = ( le ‘ 𝑉 )
mgcoval.4 ⊢ ≲ = ( le ‘ 𝑊 )
mgcval.1 ⊢ 𝐻 = ( 𝑉 MGalConn 𝑊 )
mgcval.2 ⊢ ( 𝜑 → 𝑉 ∈ Proset )
mgcval.3 ⊢ ( 𝜑 → 𝑊 ∈ Proset )
mgccole.1 ⊢ ( 𝜑 → 𝐹 𝐻 𝐺 )
Assertion mgcf1 ( 𝜑 → 𝐹 : 𝐴 ⟶ 𝐵 )

Proof

Step Hyp Ref Expression
1 mgcoval.1 ⊢ 𝐴 = ( Base ‘ 𝑉 )
2 mgcoval.2 ⊢ 𝐵 = ( Base ‘ 𝑊 )
3 mgcoval.3 ⊢ ≤ = ( le ‘ 𝑉 )
4 mgcoval.4 ⊢ ≲ = ( le ‘ 𝑊 )
5 mgcval.1 ⊢ 𝐻 = ( 𝑉 MGalConn 𝑊 )
6 mgcval.2 ⊢ ( 𝜑 → 𝑉 ∈ Proset )
7 mgcval.3 ⊢ ( 𝜑 → 𝑊 ∈ Proset )
8 mgccole.1 ⊢ ( 𝜑 → 𝐹 𝐻 𝐺 )
9 1 2 3 4 5 6 7 mgcval ⊢ ( 𝜑 → ( 𝐹 𝐻 𝐺 ↔ ( ( 𝐹 : 𝐴 ⟶ 𝐵 ∧ 𝐺 : 𝐵 ⟶ 𝐴 ) ∧ ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( ( 𝐹 ‘ 𝑥 ) ≲ 𝑦 ↔ 𝑥 ≤ ( 𝐺 ‘ 𝑦 ) ) ) ) )
10 8 9 mpbid ⊢ ( 𝜑 → ( ( 𝐹 : 𝐴 ⟶ 𝐵 ∧ 𝐺 : 𝐵 ⟶ 𝐴 ) ∧ ∀ 𝑥 ∈ 𝐴 ∀ 𝑦 ∈ 𝐵 ( ( 𝐹 ‘ 𝑥 ) ≲ 𝑦 ↔ 𝑥 ≤ ( 𝐺 ‘ 𝑦 ) ) ) )
11 10 simplld ⊢ ( 𝜑 → 𝐹 : 𝐴 ⟶ 𝐵 )