Theorem lcfl1

Description: Property of a functional with a closed kernel. (Contributed by NM, 31-Dec-2014)

	Ref	Expression
Hypotheses	lcfl1.c	⊢ 𝐶 = { 𝑓 ∈ 𝐹 ∣ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝑓 ) ) ) = ( 𝐿 ‘ 𝑓 ) }
	lcfl1.g	⊢ ( 𝜑 → 𝐺 ∈ 𝐹 )
Assertion	lcfl1	⊢ ( 𝜑 → ( 𝐺 ∈ 𝐶 ↔ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝐺 ) ) ) = ( 𝐿 ‘ 𝐺 ) ) )

Proof

Step	Hyp	Ref	Expression
1		lcfl1.c	⊢ 𝐶 = { 𝑓 ∈ 𝐹 ∣ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝑓 ) ) ) = ( 𝐿 ‘ 𝑓 ) }
2		lcfl1.g	⊢ ( 𝜑 → 𝐺 ∈ 𝐹 )
3	1	lcfl1lem	⊢ ( 𝐺 ∈ 𝐶 ↔ ( 𝐺 ∈ 𝐹 ∧ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝐺 ) ) ) = ( 𝐿 ‘ 𝐺 ) ) )
4	2	biantrurd	⊢ ( 𝜑 → ( ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝐺 ) ) ) = ( 𝐿 ‘ 𝐺 ) ↔ ( 𝐺 ∈ 𝐹 ∧ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝐺 ) ) ) = ( 𝐿 ‘ 𝐺 ) ) ) )
5	3 4	bitr4id	⊢ ( 𝜑 → ( 𝐺 ∈ 𝐶 ↔ ( ⊥ ‘ ( ⊥ ‘ ( 𝐿 ‘ 𝐺 ) ) ) = ( 𝐿 ‘ 𝐺 ) ) )