Theorem cdleme50ex 41759

Description: Part of Lemma E in [Crawley] p. 113. TODO: fix comment. (Contributed by NM, 11-Apr-2013.)

Hypotheses

Ref	Expression
cdleme.l	⊢ ≤ = (le‘𝐾)
cdleme.a	⊢ 𝐴 = (Atoms‘𝐾)
cdleme.h	⊢ 𝐻 = (LHyp‘𝐾)
cdleme.t	⊢ 𝑇 = ((LTrn‘𝐾)‘𝑊)

Assertion

Ref	Expression
cdleme50ex	⊢ (((𝐾 ∈ HL ∧ 𝑊 ∈ 𝐻) ∧ (𝑃 ∈ 𝐴 ∧ ¬ 𝑃 ≤ 𝑊) ∧ (𝑄 ∈ 𝐴 ∧ ¬ 𝑄 ≤ 𝑊)) → ∃𝑓 ∈ 𝑇 (𝑓‘𝑃) = 𝑄)

Distinct variable groups:   𝐴,𝑓   𝑓,𝐾   ≤ ,𝑓   𝑃,𝑓   𝑄,𝑓   𝑇,𝑓   𝑓,𝑊

Allowed substitution hint:   𝐻(𝑓)

Proof of Theorem cdleme50ex

Dummy variables 𝑠 𝑡 𝑥 𝑦 𝑧 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		eqid 2763	. . 3 ⊢ (Base‘𝐾) = (Base‘𝐾)
2		cdleme.l	. . 3 ⊢ ≤ = (le‘𝐾)
3		eqid 2763	. . 3 ⊢ (join‘𝐾) = (join‘𝐾)
4		eqid 2763	. . 3 ⊢ (meet‘𝐾) = (meet‘𝐾)
5		cdleme.a	. . 3 ⊢ 𝐴 = (Atoms‘𝐾)
6		cdleme.h	. . 3 ⊢ 𝐻 = (LHyp‘𝐾)
7		eqid 2763	. . 3 ⊢ ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊) = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊)
8		eqid 2763	. . 3 ⊢ ((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))) = ((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))
9		eqid 2763	. . 3 ⊢ ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))) = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))
10		eqid 2763	. . 3 ⊢ (𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥)) = (𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥))
11		cdleme.t	. . 3 ⊢ 𝑇 = ((LTrn‘𝐾)‘𝑊)
12	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11	cdleme50ltrn 41757	. 2 ⊢ (((𝐾 ∈ HL ∧ 𝑊 ∈ 𝐻) ∧ (𝑃 ∈ 𝐴 ∧ ¬ 𝑃 ≤ 𝑊) ∧ (𝑄 ∈ 𝐴 ∧ ¬ 𝑄 ≤ 𝑊)) → (𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥)) ∈ 𝑇)
13	1, 2, 3, 4, 5, 6, 7, 8, 9, 10	cdleme17d 41698	. 2 ⊢ (((𝐾 ∈ HL ∧ 𝑊 ∈ 𝐻) ∧ (𝑃 ∈ 𝐴 ∧ ¬ 𝑃 ≤ 𝑊) ∧ (𝑄 ∈ 𝐴 ∧ ¬ 𝑄 ≤ 𝑊)) → ((𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥))‘𝑃) = 𝑄)
14		fveq1 6895	. . . 4 ⊢ (𝑓 = (𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥)) → (𝑓‘𝑃) = ((𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥))‘𝑃))
15	14	eqeq1d 2765	. . 3 ⊢ (𝑓 = (𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥)) → ((𝑓‘𝑃) = 𝑄 ↔ ((𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥))‘𝑃) = 𝑄))
16	15	rspcev 3580	. 2 ⊢ (((𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥)) ∈ 𝑇 ∧ ((𝑥 ∈ (Base‘𝐾) ↦ if((𝑃 ≠ 𝑄 ∧ ¬ 𝑥 ≤ 𝑊), (℩𝑧 ∈ (Base‘𝐾)∀𝑠 ∈ 𝐴 ((¬ 𝑠 ≤ 𝑊 ∧ (𝑠(join‘𝐾)(𝑥(meet‘𝐾)𝑊)) = 𝑥) → 𝑧 = (if(𝑠 ≤ (𝑃(join‘𝐾)𝑄), (℩𝑦 ∈ (Base‘𝐾)∀𝑡 ∈ 𝐴 ((¬ 𝑡 ≤ 𝑊 ∧ ¬ 𝑡 ≤ (𝑃(join‘𝐾)𝑄)) → 𝑦 = ((𝑃(join‘𝐾)𝑄)(meet‘𝐾)(((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊)))(join‘𝐾)((𝑠(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))), ⦋𝑠 / 𝑡⦌((𝑡(join‘𝐾)((𝑃(join‘𝐾)𝑄)(meet‘𝐾)𝑊))(meet‘𝐾)(𝑄(join‘𝐾)((𝑃(join‘𝐾)𝑡)(meet‘𝐾)𝑊))))(join‘𝐾)(𝑥(meet‘𝐾)𝑊)))), 𝑥))‘𝑃) = 𝑄) → ∃𝑓 ∈ 𝑇 (𝑓‘𝑃) = 𝑄)
17	12, 13, 16	syl2anc 596	1 ⊢ (((𝐾 ∈ HL ∧ 𝑊 ∈ 𝐻) ∧ (𝑃 ∈ 𝐴 ∧ ¬ 𝑃 ≤ 𝑊) ∧ (𝑄 ∈ 𝐴 ∧ ¬ 𝑄 ≤ 𝑊)) → ∃𝑓 ∈ 𝑇 (𝑓‘𝑃) = 𝑄)

This proof depends on syntax axioms:  ¬ wn 3   → wi 4   ∧ wa 401   ∧ w3a 1103   = wceq 1569   ∈ wcel 2146   ≠ wne 2959  ∀wral 3080  ∃wrex 3090  ⦋csb 3851  ifcif 4485   class class class wbr 5106   ↦ cmpt 5189  ‘cfv 6547  ℩crio 7386  (class class class)co 7430  Basecbs 17402  lecple 17450  joincjn 18500  meetcmee 18501  Atomscatm 40463  HLchlt 40550  LHypclh 41184  LTrncltrn 41301

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1827  ax-4 1841  ax-5 1944  ax-6 2001  ax-7 2042  ax-8 2148  ax-9 2156  ax-10 2179  ax-11 2196  ax-12 2215  ax-ext 2735  ax-rep 5235  ax-sep 5252  ax-nul 5263  ax-pow 5331  ax-pr 5395  ax-un 7761  ax-riotaBAD 40153

This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-3an 1105  df-tru 1572  df-fal 1582  df-ex 1812  df-nf 1816  df-sb 2101  df-mo 2567  df-eu 2597  df-clab 2742  df-cleq 2755  df-clel 2839  df-nfc 2913  df-ne 2960  df-ral 3081  df-rex 3091  df-rmo 3369  df-reu 3370  df-rab 3417  df-v 3456  df-sbc 3743  df-csb 3852  df-ss 3901  df-dif 4050  df-in 4094  df-un 4154  df-nul 4282  df-if 4486  df-pw 4562  df-sn 4589  df-pr 4591  df-op 4839  df-uni 4871  df-iun 4956  df-iin 4957  df-br 5107  df-opab 5171  df-mpt 5190  df-id 5550  df-xp 5661  df-rel 5662  df-cnv 5663  df-co 5664  df-dm 5665  df-rn 5666  df-res 5667  df-ima 5668  df-iota 6501  df-fun 6549  df-fn 6550  df-f 6551  df-f1 6552  df-fo 6553  df-f1o 6554  df-fv 6555  df-riota 7387  df-ov 7433  df-oprab 7434  df-mpo 7435  df-1st 8011  df-2nd 8012  df-undef 8304  df-map 8863  df-proset 18483  df-poset 18502  df-plt 18517  df-lub 18533  df-glb 18534  df-join 18535  df-meet 18536  df-p0 18612  df-p1 18613  df-lat 18621  df-clat 18688  df-oposet 40376  df-ol 40378  df-oml 40379  df-covers 40466  df-ats 40467  df-atl 40498  df-cvlat 40522  df-hlat 40551  df-llines 40698  df-lplanes 40699  df-lvols 40700  df-lines 40701  df-psubsp 40703  df-pmap 40704  df-padd 40996  df-lhyp 41188  df-laut 41189  df-ldil 41304  df-ltrn 41305

This theorem is used by:  cdleme  41760  cdlemf  41763  dia2dimlem6  42269