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| Type | Label | Description |
|---|---|---|
| Statement | ||
| Theorem | knoppcnlem8 36501* | Lemma for knoppcn 36505. (Contributed by Asger C. Ipsen, 4-Apr-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) ⇒ ⊢ (𝜑 → seq0( ∘f + , (𝑚 ∈ ℕ0 ↦ (𝑧 ∈ ℝ ↦ ((𝐹‘𝑧)‘𝑚)))):ℕ0⟶(ℂ ↑m ℝ)) | ||
| Theorem | knoppcnlem9 36502* | Lemma for knoppcn 36505. (Contributed by Asger C. Ipsen, 4-Apr-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) & ⊢ (𝜑 → (abs‘𝐶) < 1) ⇒ ⊢ (𝜑 → seq0( ∘f + , (𝑚 ∈ ℕ0 ↦ (𝑧 ∈ ℝ ↦ ((𝐹‘𝑧)‘𝑚))))(⇝𝑢‘ℝ)𝑊) | ||
| Theorem | knoppcnlem10 36503* | Lemma for knoppcn 36505. (Contributed by Asger C. Ipsen, 4-Apr-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) Avoid ax-mulf 11235. (Revised by GG, 19-Apr-2025.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) & ⊢ (𝜑 → 𝑀 ∈ ℕ0) ⇒ ⊢ (𝜑 → (𝑧 ∈ ℝ ↦ ((𝐹‘𝑧)‘𝑀)) ∈ ((topGen‘ran (,)) Cn (TopOpen‘ℂfld))) | ||
| Theorem | knoppcnlem11 36504* | Lemma for knoppcn 36505. (Contributed by Asger C. Ipsen, 4-Apr-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) ⇒ ⊢ (𝜑 → seq0( ∘f + , (𝑚 ∈ ℕ0 ↦ (𝑧 ∈ ℝ ↦ ((𝐹‘𝑧)‘𝑚)))):ℕ0⟶(ℝ–cn→ℂ)) | ||
| Theorem | knoppcn 36505* | The continuous nowhere differentiable function 𝑊 ( Knopp, K. (1918). Math. Z. 2, 1-26 ) is, in fact, continuous. (Contributed by Asger C. Ipsen, 4-Apr-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) & ⊢ (𝜑 → (abs‘𝐶) < 1) ⇒ ⊢ (𝜑 → 𝑊 ∈ (ℝ–cn→ℂ)) | ||
| Theorem | knoppcld 36506* | Closure theorem for Knopp's function. (Contributed by Asger C. Ipsen, 26-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) & ⊢ (𝜑 → (abs‘𝐶) < 1) ⇒ ⊢ (𝜑 → (𝑊‘𝐴) ∈ ℂ) | ||
| Theorem | unblimceq0lem 36507* | Lemma for unblimceq0 36508. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ (𝜑 → 𝑆 ⊆ ℂ) & ⊢ (𝜑 → 𝐹:𝑆⟶ℂ) & ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → ∀𝑏 ∈ ℝ+ ∀𝑑 ∈ ℝ+ ∃𝑥 ∈ 𝑆 ((abs‘(𝑥 − 𝐴)) < 𝑑 ∧ 𝑏 ≤ (abs‘(𝐹‘𝑥)))) ⇒ ⊢ (𝜑 → ∀𝑐 ∈ ℝ+ ∀𝑑 ∈ ℝ+ ∃𝑦 ∈ 𝑆 (𝑦 ≠ 𝐴 ∧ (abs‘(𝑦 − 𝐴)) < 𝑑 ∧ 𝑐 ≤ (abs‘(𝐹‘𝑦)))) | ||
| Theorem | unblimceq0 36508* | If 𝐹 is unbounded near 𝐴 it has no limit at 𝐴. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ (𝜑 → 𝑆 ⊆ ℂ) & ⊢ (𝜑 → 𝐹:𝑆⟶ℂ) & ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → ∀𝑏 ∈ ℝ+ ∀𝑑 ∈ ℝ+ ∃𝑥 ∈ 𝑆 ((abs‘(𝑥 − 𝐴)) < 𝑑 ∧ 𝑏 ≤ (abs‘(𝐹‘𝑥)))) ⇒ ⊢ (𝜑 → (𝐹 limℂ 𝐴) = ∅) | ||
| Theorem | unbdqndv1 36509* | If the difference quotient (((𝐹‘𝑧) − (𝐹‘𝐴)) / (𝑧 − 𝐴)) is unbounded near 𝐴 then 𝐹 is not differentiable at 𝐴. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ 𝐺 = (𝑧 ∈ (𝑋 ∖ {𝐴}) ↦ (((𝐹‘𝑧) − (𝐹‘𝐴)) / (𝑧 − 𝐴))) & ⊢ (𝜑 → 𝑆 ⊆ ℂ) & ⊢ (𝜑 → 𝑋 ⊆ 𝑆) & ⊢ (𝜑 → 𝐹:𝑋⟶ℂ) & ⊢ (𝜑 → ∀𝑏 ∈ ℝ+ ∀𝑑 ∈ ℝ+ ∃𝑥 ∈ (𝑋 ∖ {𝐴})((abs‘(𝑥 − 𝐴)) < 𝑑 ∧ 𝑏 ≤ (abs‘(𝐺‘𝑥)))) ⇒ ⊢ (𝜑 → ¬ 𝐴 ∈ dom (𝑆 D 𝐹)) | ||
| Theorem | unbdqndv2lem1 36510 | Lemma for unbdqndv2 36512. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ (𝜑 → 𝐴 ∈ ℂ) & ⊢ (𝜑 → 𝐵 ∈ ℂ) & ⊢ (𝜑 → 𝐶 ∈ ℂ) & ⊢ (𝜑 → 𝐷 ∈ ℂ) & ⊢ (𝜑 → 𝐸 ∈ ℝ+) & ⊢ (𝜑 → 𝐷 ≠ 0) & ⊢ (𝜑 → (2 · 𝐸) ≤ (abs‘((𝐴 − 𝐵) / 𝐷))) ⇒ ⊢ (𝜑 → ((𝐸 · (abs‘𝐷)) ≤ (abs‘(𝐴 − 𝐶)) ∨ (𝐸 · (abs‘𝐷)) ≤ (abs‘(𝐵 − 𝐶)))) | ||
| Theorem | unbdqndv2lem2 36511* | Lemma for unbdqndv2 36512. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ 𝐺 = (𝑧 ∈ (𝑋 ∖ {𝐴}) ↦ (((𝐹‘𝑧) − (𝐹‘𝐴)) / (𝑧 − 𝐴))) & ⊢ 𝑊 = if((𝐵 · (𝑉 − 𝑈)) ≤ (abs‘((𝐹‘𝑈) − (𝐹‘𝐴))), 𝑈, 𝑉) & ⊢ (𝜑 → 𝑋 ⊆ ℝ) & ⊢ (𝜑 → 𝐹:𝑋⟶ℂ) & ⊢ (𝜑 → 𝐴 ∈ 𝑋) & ⊢ (𝜑 → 𝐵 ∈ ℝ+) & ⊢ (𝜑 → 𝐷 ∈ ℝ+) & ⊢ (𝜑 → 𝑈 ∈ 𝑋) & ⊢ (𝜑 → 𝑉 ∈ 𝑋) & ⊢ (𝜑 → 𝑈 ≠ 𝑉) & ⊢ (𝜑 → 𝑈 ≤ 𝐴) & ⊢ (𝜑 → 𝐴 ≤ 𝑉) & ⊢ (𝜑 → (𝑉 − 𝑈) < 𝐷) & ⊢ (𝜑 → (2 · 𝐵) ≤ ((abs‘((𝐹‘𝑉) − (𝐹‘𝑈))) / (𝑉 − 𝑈))) ⇒ ⊢ (𝜑 → (𝑊 ∈ (𝑋 ∖ {𝐴}) ∧ ((abs‘(𝑊 − 𝐴)) < 𝐷 ∧ 𝐵 ≤ (abs‘(𝐺‘𝑊))))) | ||
| Theorem | unbdqndv2 36512* | Variant of unbdqndv1 36509 with the hypothesis that (((𝐹‘𝑦) − (𝐹‘𝑥)) / (𝑦 − 𝑥)) is unbounded where 𝑥 ≤ 𝐴 and 𝐴 ≤ 𝑦. (Contributed by Asger C. Ipsen, 12-May-2021.) |
| ⊢ (𝜑 → 𝑋 ⊆ ℝ) & ⊢ (𝜑 → 𝐹:𝑋⟶ℂ) & ⊢ (𝜑 → ∀𝑏 ∈ ℝ+ ∀𝑑 ∈ ℝ+ ∃𝑥 ∈ 𝑋 ∃𝑦 ∈ 𝑋 ((𝑥 ≤ 𝐴 ∧ 𝐴 ≤ 𝑦) ∧ ((𝑦 − 𝑥) < 𝑑 ∧ 𝑥 ≠ 𝑦) ∧ 𝑏 ≤ ((abs‘((𝐹‘𝑦) − (𝐹‘𝑥))) / (𝑦 − 𝑥)))) ⇒ ⊢ (𝜑 → ¬ 𝐴 ∈ dom (ℝ D 𝐹)) | ||
| Theorem | knoppndvlem1 36513 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐽 ∈ ℤ) & ⊢ (𝜑 → 𝑀 ∈ ℤ) ⇒ ⊢ (𝜑 → ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) ∈ ℝ) | ||
| Theorem | knoppndvlem2 36514 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐼 ∈ ℤ) & ⊢ (𝜑 → 𝐽 ∈ ℤ) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝐽 < 𝐼) ⇒ ⊢ (𝜑 → (((2 · 𝑁)↑𝐼) · ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀)) ∈ ℤ) | ||
| Theorem | knoppndvlem3 36515 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) |
| ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) ⇒ ⊢ (𝜑 → (𝐶 ∈ ℝ ∧ (abs‘𝐶) < 1)) | ||
| Theorem | knoppndvlem4 36516* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → seq0( + , (𝐹‘𝐴)) ⇝ (𝑊‘𝐴)) | ||
| Theorem | knoppndvlem5 36517* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝐶 ∈ ℝ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → Σ𝑖 ∈ (0...𝐽)((𝐹‘𝐴)‘𝑖) ∈ ℝ) | ||
| Theorem | knoppndvlem6 36518* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝑊‘𝐴) = Σ𝑖 ∈ (0...𝐽)((𝐹‘𝐴)‘𝑖)) | ||
| Theorem | knoppndvlem7 36519* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → ((𝐹‘𝐴)‘𝐽) = ((𝐶↑𝐽) · (𝑇‘(𝑀 / 2)))) | ||
| Theorem | knoppndvlem8 36520* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 2 ∥ 𝑀) ⇒ ⊢ (𝜑 → ((𝐹‘𝐴)‘𝐽) = 0) | ||
| Theorem | knoppndvlem9 36521* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → ¬ 2 ∥ 𝑀) ⇒ ⊢ (𝜑 → ((𝐹‘𝐴)‘𝐽) = ((𝐶↑𝐽) / 2)) | ||
| Theorem | knoppndvlem10 36522* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 15-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑀 + 1)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → (abs‘(((𝐹‘𝐵)‘𝐽) − ((𝐹‘𝐴)‘𝐽))) = (((abs‘𝐶)↑𝐽) / 2)) | ||
| Theorem | knoppndvlem11 36523* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 28-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ (𝜑 → 𝐴 ∈ ℝ) & ⊢ (𝜑 → 𝐵 ∈ ℝ) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → (abs‘(Σ𝑖 ∈ (0...(𝐽 − 1))((𝐹‘𝐵)‘𝑖) − Σ𝑖 ∈ (0...(𝐽 − 1))((𝐹‘𝐴)‘𝑖))) ≤ ((abs‘(𝐵 − 𝐴)) · Σ𝑖 ∈ (0...(𝐽 − 1))(((2 · 𝑁) · (abs‘𝐶))↑𝑖))) | ||
| Theorem | knoppndvlem12 36524 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 29-Jun-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → (((2 · 𝑁) · (abs‘𝐶)) ≠ 1 ∧ 1 < (((2 · 𝑁) · (abs‘𝐶)) − 1))) | ||
| Theorem | knoppndvlem13 36525 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 1-Jul-2021.) (Revised by Asger C. Ipsen, 5-Jul-2021.) |
| ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → 𝐶 ≠ 0) | ||
| Theorem | knoppndvlem14 36526* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 1-Jul-2021.) (Revised by Asger C. Ipsen, 7-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑀 + 1)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → (abs‘(Σ𝑖 ∈ (0...(𝐽 − 1))((𝐹‘𝐵)‘𝑖) − Σ𝑖 ∈ (0...(𝐽 − 1))((𝐹‘𝐴)‘𝑖))) ≤ ((((abs‘𝐶)↑𝐽) / 2) · (1 / (((2 · 𝑁) · (abs‘𝐶)) − 1)))) | ||
| Theorem | knoppndvlem15 36527* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 6-Jul-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑀 + 1)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → ((((abs‘𝐶)↑𝐽) / 2) · (1 − (1 / (((2 · 𝑁) · (abs‘𝐶)) − 1)))) ≤ (abs‘((𝑊‘𝐵) − (𝑊‘𝐴)))) | ||
| Theorem | knoppndvlem16 36528 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 19-Jul-2021.) |
| ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑀 + 1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → (𝐵 − 𝐴) = (((2 · 𝑁)↑-𝐽) / 2)) | ||
| Theorem | knoppndvlem17 36529* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 12-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑀) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑀 + 1)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑀 ∈ ℤ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → ((((2 · 𝑁) · (abs‘𝐶))↑𝐽) · (1 − (1 / (((2 · 𝑁) · (abs‘𝐶)) − 1)))) ≤ ((abs‘((𝑊‘𝐵) − (𝑊‘𝐴))) / (𝐵 − 𝐴))) | ||
| Theorem | knoppndvlem18 36530* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 14-Aug-2021.) |
| ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐷 ∈ ℝ+) & ⊢ (𝜑 → 𝐸 ∈ ℝ+) & ⊢ (𝜑 → 𝐺 ∈ ℝ+) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → ∃𝑗 ∈ ℕ0 ((((2 · 𝑁)↑-𝑗) / 2) < 𝐷 ∧ 𝐸 ≤ ((((2 · 𝑁) · (abs‘𝐶))↑𝑗) · 𝐺))) | ||
| Theorem | knoppndvlem19 36531* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 17-Aug-2021.) |
| ⊢ 𝐴 = ((((2 · 𝑁)↑-𝐽) / 2) · 𝑚) & ⊢ 𝐵 = ((((2 · 𝑁)↑-𝐽) / 2) · (𝑚 + 1)) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝐻 ∈ ℝ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → ∃𝑚 ∈ ℤ (𝐴 ≤ 𝐻 ∧ 𝐻 ≤ 𝐵)) | ||
| Theorem | knoppndvlem20 36532 | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 18-Aug-2021.) |
| ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → (1 − (1 / (((2 · 𝑁) · (abs‘𝐶)) − 1))) ∈ ℝ+) | ||
| Theorem | knoppndvlem21 36533* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 18-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ 𝐺 = (1 − (1 / (((2 · 𝑁) · (abs‘𝐶)) − 1))) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐷 ∈ ℝ+) & ⊢ (𝜑 → 𝐸 ∈ ℝ+) & ⊢ (𝜑 → 𝐻 ∈ ℝ) & ⊢ (𝜑 → 𝐽 ∈ ℕ0) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) & ⊢ (𝜑 → (((2 · 𝑁)↑-𝐽) / 2) < 𝐷) & ⊢ (𝜑 → 𝐸 ≤ ((((2 · 𝑁) · (abs‘𝐶))↑𝐽) · 𝐺)) ⇒ ⊢ (𝜑 → ∃𝑎 ∈ ℝ ∃𝑏 ∈ ℝ ((𝑎 ≤ 𝐻 ∧ 𝐻 ≤ 𝑏) ∧ ((𝑏 − 𝑎) < 𝐷 ∧ 𝑎 ≠ 𝑏) ∧ 𝐸 ≤ ((abs‘((𝑊‘𝑏) − (𝑊‘𝑎))) / (𝑏 − 𝑎)))) | ||
| Theorem | knoppndvlem22 36534* | Lemma for knoppndv 36535. (Contributed by Asger C. Ipsen, 19-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝐷 ∈ ℝ+) & ⊢ (𝜑 → 𝐸 ∈ ℝ+) & ⊢ (𝜑 → 𝐻 ∈ ℝ) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → ∃𝑎 ∈ ℝ ∃𝑏 ∈ ℝ ((𝑎 ≤ 𝐻 ∧ 𝐻 ≤ 𝑏) ∧ ((𝑏 − 𝑎) < 𝐷 ∧ 𝑎 ≠ 𝑏) ∧ 𝐸 ≤ ((abs‘((𝑊‘𝑏) − (𝑊‘𝑎))) / (𝑏 − 𝑎)))) | ||
| Theorem | knoppndv 36535* | The continuous nowhere differentiable function 𝑊 ( Knopp, K. (1918). Math. Z. 2, 1-26 ) is, in fact, nowhere differentiable. (Contributed by Asger C. Ipsen, 19-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 1 < (𝑁 · (abs‘𝐶))) ⇒ ⊢ (𝜑 → dom (ℝ D 𝑊) = ∅) | ||
| Theorem | knoppf 36536* | Knopp's function is a function. (Contributed by Asger C. Ipsen, 25-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) ⇒ ⊢ (𝜑 → 𝑊:ℝ⟶ℝ) | ||
| Theorem | knoppcn2 36537* | Variant of knoppcn 36505 with different codomain. (Contributed by Asger C. Ipsen, 25-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ ((𝐶↑𝑛) · (𝑇‘(((2 · 𝑁)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) & ⊢ (𝜑 → 𝑁 ∈ ℕ) & ⊢ (𝜑 → 𝐶 ∈ (-1(,)1)) ⇒ ⊢ (𝜑 → 𝑊 ∈ (ℝ–cn→ℝ)) | ||
| Theorem | cnndvlem1 36538* | Lemma for cnndv 36540. (Contributed by Asger C. Ipsen, 25-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ (((1 / 2)↑𝑛) · (𝑇‘(((2 · 3)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) ⇒ ⊢ (𝑊 ∈ (ℝ–cn→ℝ) ∧ dom (ℝ D 𝑊) = ∅) | ||
| Theorem | cnndvlem2 36539* | Lemma for cnndv 36540. (Contributed by Asger C. Ipsen, 26-Aug-2021.) |
| ⊢ 𝑇 = (𝑥 ∈ ℝ ↦ (abs‘((⌊‘(𝑥 + (1 / 2))) − 𝑥))) & ⊢ 𝐹 = (𝑦 ∈ ℝ ↦ (𝑛 ∈ ℕ0 ↦ (((1 / 2)↑𝑛) · (𝑇‘(((2 · 3)↑𝑛) · 𝑦))))) & ⊢ 𝑊 = (𝑤 ∈ ℝ ↦ Σ𝑖 ∈ ℕ0 ((𝐹‘𝑤)‘𝑖)) ⇒ ⊢ ∃𝑓(𝑓 ∈ (ℝ–cn→ℝ) ∧ dom (ℝ D 𝑓) = ∅) | ||
| Theorem | cnndv 36540 | There exists a continuous nowhere differentiable function. The result follows directly from knoppcn 36505 and knoppndv 36535. (Contributed by Asger C. Ipsen, 26-Aug-2021.) |
| ⊢ ∃𝑓(𝑓 ∈ (ℝ–cn→ℝ) ∧ dom (ℝ D 𝑓) = ∅) | ||
In this mathbox, we try to respect the ordering of the sections of the main part. There are strengthenings of theorems of the main part, as well as work on reducing axiom dependencies. | ||
Miscellaneous utility theorems of propositional calculus. | ||
In this section, we prove a few rules of inference derived from modus ponens ax-mp 5, and which do not depend on any other axioms. | ||
| Theorem | bj-mp2c 36541 | A double modus ponens inference. Inference associated with mpd 15. (Contributed by BJ, 24-Sep-2019.) |
| ⊢ 𝜑 & ⊢ (𝜑 → 𝜓) & ⊢ (𝜑 → (𝜓 → 𝜒)) ⇒ ⊢ 𝜒 | ||
| Theorem | bj-mp2d 36542 | A double modus ponens inference. Inference associated with mpcom 38. (Contributed by BJ, 24-Sep-2019.) |
| ⊢ 𝜑 & ⊢ (𝜑 → 𝜓) & ⊢ (𝜓 → (𝜑 → 𝜒)) ⇒ ⊢ 𝜒 | ||
In this section, we prove a syntactic theorem (bj-0 36543) asserting that some formula is well-formed. Then, we use this syntactic theorem to shorten the proof of a "usual" theorem (bj-1 36544) and explain in the comment of that theorem why this phenomenon is unusual. | ||
| Theorem | bj-0 36543 | A syntactic theorem. See the section comment and the comment of bj-1 36544. The full proof (that is, with the syntactic, non-essential steps) does not appear on this webpage. It has five steps and reads $= wph wps wi wch wi $. The only other syntactic theorems in the main part of set.mm are wel 2109 and weq 1962. (Contributed by BJ, 24-Sep-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| wff ((𝜑 → 𝜓) → 𝜒) | ||
| Theorem | bj-1 36544 |
In this proof, the use of the syntactic theorem bj-0 36543
allows to reduce
the total length by one (non-essential) step. See also the section
comment and the comment of bj-0 36543. Since bj-0 36543
is used in a
non-essential step, this use does not appear on this webpage (but the
present theorem appears on the webpage for bj-0 36543
as a theorem referencing
it). The full proof reads $= wph wps wch bj-0 id $. (while, without
using bj-0 36543, it would read $= wph wps wi wch wi id $.).
Now we explain why syntactic theorems are not useful in set.mm. Suppose that the syntactic theorem thm-0 proves that PHI is a well-formed formula, and that thm-0 is used to shorten the proof of thm-1. Assume that PHI does have proper non-atomic subformulas (which is not the case of the formula proved by weq 1962 or wel 2109). Then, the proof of thm-1 does not construct all the proper non-atomic subformulas of PHI (if it did, then using thm-0 would not shorten it). Therefore, thm-1 is a special instance of a more general theorem with essentially the same proof. In the present case, bj-1 36544 is a special instance of id 22. (Contributed by BJ, 24-Sep-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ (((𝜑 → 𝜓) → 𝜒) → ((𝜑 → 𝜓) → 𝜒)) | ||
| Theorem | bj-a1k 36545 | Weakening of ax-1 6. As a consequence, its associated inference is an instance (where we allow extra hypotheses) of ax-1 6. Its commuted form is 2a1 28 (but bj-a1k 36545 does not require ax-2 7). This shortens the proofs of dfwe2 7794 (937>925), ordunisuc2 7865 (789>777), r111 9815 (558>545), smo11 8404 (1176>1164). (Contributed by BJ, 11-Aug-2020.) (Proof modification is discouraged.) |
| ⊢ (𝜑 → (𝜓 → (𝜒 → 𝜓))) | ||
| Theorem | bj-poni 36546 | Inference associated with "pon", pm2.27 42. Its associated inference is ax-mp 5. (Contributed by BJ, 30-Jul-2024.) |
| ⊢ 𝜑 ⇒ ⊢ ((𝜑 → 𝜓) → 𝜓) | ||
| Theorem | bj-nnclav 36547 | When ⊥ is substituted for 𝜓, this formula is the Clavius law with a doubly negated consequent, which is therefore a minimalistic tautology. Notice the non-intuitionistic proof from peirce 202 and pm2.27 42 chained using syl 17. (Contributed by BJ, 4-Dec-2023.) |
| ⊢ (((𝜑 → 𝜓) → 𝜑) → ((𝜑 → 𝜓) → 𝜓)) | ||
| Theorem | bj-nnclavi 36548 | Inference associated with bj-nnclav 36547. Its associated inference is an instance of syl 17. Notice the non-intuitionistic proof from bj-peircei 36566 and bj-poni 36546. (Contributed by BJ, 30-Jul-2024.) |
| ⊢ ((𝜑 → 𝜓) → 𝜑) ⇒ ⊢ ((𝜑 → 𝜓) → 𝜓) | ||
| Theorem | bj-nnclavc 36549 | Commuted form of bj-nnclav 36547. Notice the non-intuitionistic proof from bj-peircei 36566 and imim1i 63. (Contributed by BJ, 30-Jul-2024.) A proof which is shorter when compressed uses embantd 59. (Proof modification is discouraged.) |
| ⊢ ((𝜑 → 𝜓) → (((𝜑 → 𝜓) → 𝜑) → 𝜓)) | ||
| Theorem | bj-nnclavci 36550 | Inference associated with bj-nnclavc 36549. Its associated inference is an instance of syl 17. Notice the non-intuitionistic proof from peirce 202 and syl 17. (Contributed by BJ, 30-Jul-2024.) |
| ⊢ (𝜑 → 𝜓) ⇒ ⊢ (((𝜑 → 𝜓) → 𝜑) → 𝜓) | ||
| Theorem | bj-jarrii 36551 | Inference associated with jarri 107. Contrary to it, it does not require ax-2 7, but only ax-mp 5 and ax-1 6. (Contributed by BJ, 29-Mar-2020.) (Proof modification is discouraged.) |
| ⊢ ((𝜑 → 𝜓) → 𝜒) & ⊢ 𝜓 ⇒ ⊢ 𝜒 | ||
| Theorem | bj-imim21 36552 | The propositional function (𝜒 → (. → 𝜃)) is decreasing. (Contributed by BJ, 19-Jul-2019.) |
| ⊢ ((𝜑 → 𝜓) → ((𝜒 → (𝜓 → 𝜃)) → (𝜒 → (𝜑 → 𝜃)))) | ||
| Theorem | bj-imim21i 36553 | Inference associated with bj-imim21 36552. Its associated inference is syl5 34. (Contributed by BJ, 19-Jul-2019.) |
| ⊢ (𝜑 → 𝜓) ⇒ ⊢ ((𝜒 → (𝜓 → 𝜃)) → (𝜒 → (𝜑 → 𝜃))) | ||
| Theorem | bj-peircestab 36554 | Over minimal implicational calculus, Peirce's law implies the double negation of the stability of any formula (that is the interpretation when ⊥ is substituted for 𝜓 and for 𝜒). Therefore, the double negation of the stability of any formula is provable in classical refutability calculus. It is also provable in intuitionistic calculus (see iset.mm/bj-nnst) but it is not provable in minimal calculus (see bj-stabpeirce 36555). (Contributed by BJ, 30-Nov-2023.) Axiom ax-3 8 is only used through Peirce's law peirce 202. (Proof modification is discouraged.) |
| ⊢ (((((𝜑 → 𝜓) → 𝜒) → 𝜑) → 𝜒) → 𝜒) | ||
| Theorem | bj-stabpeirce 36555 | This minimal implicational calculus tautology is used in the following argument: When 𝜑, 𝜓, 𝜒, 𝜃, 𝜏 are replaced respectively by (𝜑 → ⊥), ⊥, 𝜑, ⊥, ⊥, the antecedent becomes ¬ ¬ (¬ ¬ 𝜑 → 𝜑), that is, the double negation of the stability of 𝜑. If that statement were provable in minimal calculus, then, since ⊥ plays no particular role in minimal calculus, also the statement with 𝜓 in place of ⊥ would be provable. The corresponding consequent is (((𝜓 → 𝜑) → 𝜓) → 𝜓), that is, the non-intuitionistic Peirce law. Therefore, the double negation of the stability of any formula is not provable in minimal calculus. However, it is provable both in intuitionistic calculus (see iset.mm/bj-nnst) and in classical refutability calculus (see bj-peircestab 36554). (Contributed by BJ, 30-Nov-2023.) (Revised by BJ, 30-Jul-2024.) (Proof modification is discouraged.) |
| ⊢ (((((𝜑 → 𝜓) → 𝜒) → 𝜃) → 𝜏) → (((𝜓 → 𝜒) → 𝜃) → 𝜏)) | ||
Positive calculus is understood to be intuitionistic. | ||
| Theorem | bj-syl66ib 36556 | A mixed syllogism inference derived from imbitrdi 251. In addition to bj-dvelimdv1 36853, it can also shorten alexsubALTlem4 24058 (4821>4812), supsrlem 11151 (2868>2863). (Contributed by BJ, 20-Oct-2021.) |
| ⊢ (𝜑 → (𝜓 → 𝜃)) & ⊢ (𝜃 → 𝜏) & ⊢ (𝜏 ↔ 𝜒) ⇒ ⊢ (𝜑 → (𝜓 → 𝜒)) | ||
| Theorem | bj-orim2 36557 | Proof of orim2 970 from the axiomatic definition of disjunction (olc 869, orc 868, jao 963) and minimal implicational calculus. (Contributed by BJ, 4-Apr-2021.) (Proof modification is discouraged.) |
| ⊢ ((𝜑 → 𝜓) → ((𝜒 ∨ 𝜑) → (𝜒 ∨ 𝜓))) | ||
| Theorem | bj-currypeirce 36558 | Curry's axiom curryax 894 (a non-intuitionistic positive statement sometimes called a paradox of material implication) implies Peirce's axiom peirce 202 over minimal implicational calculus and the axiomatic definition of disjunction (actually, only the elimination axiom jao 963 via its inference form jaoi 858; the introduction axioms olc 869 and orc 868 are not needed). Note that this theorem shows that actually, the standard instance of curryax 894 implies the standard instance of peirce 202, which is not the case for the converse bj-peircecurry 36559. (Contributed by BJ, 15-Jun-2021.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((𝜑 ∨ (𝜑 → 𝜓)) → (((𝜑 → 𝜓) → 𝜑) → 𝜑)) | ||
| Theorem | bj-peircecurry 36559 | Peirce's axiom peirce 202 implies Curry's axiom curryax 894 over minimal implicational calculus and the axiomatic definition of disjunction (actually, only the introduction axioms olc 869 and orc 868; the elimination axiom jao 963 is not needed). See bj-currypeirce 36558 for the converse. (Contributed by BJ, 15-Jun-2021.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ (𝜑 ∨ (𝜑 → 𝜓)) | ||
| Theorem | bj-animbi 36560 | Conjunction in terms of implication and biconditional. Note that the proof is intuitionistic (use of ax-3 8 comes from the unusual definition of the biconditional in set.mm). (Contributed by BJ, 23-Sep-2023.) |
| ⊢ ((𝜑 ∧ 𝜓) ↔ (𝜑 ↔ (𝜑 → 𝜓))) | ||
| Theorem | bj-currypara 36561 | Curry's paradox. Note that the proof is intuitionistic (use of ax-3 8 comes from the unusual definition of the biconditional in set.mm). The paradox comes from the case where 𝜑 is the self-referential sentence "If this sentence is true, then 𝜓", so that one can prove everything. Therefore, a consistent system cannot allow the formation of such self-referential sentences. This has lead to the study of logics rejecting contraction pm2.43 56, such as affine logic and linear logic. (Contributed by BJ, 23-Sep-2023.) (Proof modification is discouraged.) |
| ⊢ ((𝜑 ↔ (𝜑 → 𝜓)) → 𝜓) | ||
| Theorem | bj-con2com 36562 | A commuted form of the contrapositive, true in minimal calculus. (Contributed by BJ, 19-Mar-2020.) |
| ⊢ (𝜑 → ((𝜓 → ¬ 𝜑) → ¬ 𝜓)) | ||
| Theorem | bj-con2comi 36563 | Inference associated with bj-con2com 36562. Its associated inference is mt2 200. TODO: when in the main part, add to mt2 200 that it is the inference associated with bj-con2comi 36563. (Contributed by BJ, 19-Mar-2020.) |
| ⊢ 𝜑 ⇒ ⊢ ((𝜓 → ¬ 𝜑) → ¬ 𝜓) | ||
| Theorem | bj-nimn 36564 | If a formula is true, then it does not imply its negation. (Contributed by BJ, 19-Mar-2020.) A shorter proof is possible using id 22 and jc 161, however, the present proof uses theorems that are more basic than jc 161. (Proof modification is discouraged.) |
| ⊢ (𝜑 → ¬ (𝜑 → ¬ 𝜑)) | ||
| Theorem | bj-nimni 36565 | Inference associated with bj-nimn 36564. (Contributed by BJ, 19-Mar-2020.) |
| ⊢ 𝜑 ⇒ ⊢ ¬ (𝜑 → ¬ 𝜑) | ||
| Theorem | bj-peircei 36566 | Inference associated with peirce 202. (Contributed by BJ, 30-Mar-2020.) |
| ⊢ ((𝜑 → 𝜓) → 𝜑) ⇒ ⊢ 𝜑 | ||
| Theorem | bj-looinvi 36567 | Inference associated with looinv 203. Its associated inference is bj-looinvii 36568. (Contributed by BJ, 30-Mar-2020.) |
| ⊢ ((𝜑 → 𝜓) → 𝜓) ⇒ ⊢ ((𝜓 → 𝜑) → 𝜑) | ||
| Theorem | bj-looinvii 36568 | Inference associated with bj-looinvi 36567. (Contributed by BJ, 30-Mar-2020.) |
| ⊢ ((𝜑 → 𝜓) → 𝜓) & ⊢ (𝜓 → 𝜑) ⇒ ⊢ 𝜑 | ||
| Theorem | bj-mt2bi 36569 | Version of mt2 200 where the major premise is a biconditional. Another proof is also possible via con2bii 357 and mpbi 230. The current mt2bi 363 should be relabeled, maybe to imfal. (Contributed by BJ, 5-Oct-2024.) |
| ⊢ 𝜑 & ⊢ (𝜓 ↔ ¬ 𝜑) ⇒ ⊢ ¬ 𝜓 | ||
| Theorem | bj-ntrufal 36570 | The negation of a theorem is equivalent to false. This can shorten dfnul2 4336. (Contributed by BJ, 5-Oct-2024.) |
| ⊢ 𝜑 ⇒ ⊢ (¬ 𝜑 ↔ ⊥) | ||
| Theorem | bj-fal 36571 | Shortening of fal 1554 using bj-mt2bi 36569. (Contributed by Anthony Hart, 22-Oct-2010.) (Proof shortened by Mel L. O'Cat, 11-Mar-2012.) (Proof modification is discouraged.) |
| ⊢ ¬ ⊥ | ||
A few lemmas about disjunction. The fundamental theorems in this family are the dual statements pm4.71 557 and pm4.72 952. See also biort 936 and biorf 937. | ||
| Theorem | bj-jaoi1 36572 | Shortens orfa2 38093 (58>53), pm1.2 904 (20>18), pm1.2 904 (20>18), pm2.4 907 (31>25), pm2.41 908 (31>25), pm2.42 945 (38>32), pm3.2ni 881 (43>39), pm4.44 999 (55>51). (Contributed by BJ, 30-Sep-2019.) |
| ⊢ (𝜑 → 𝜓) ⇒ ⊢ ((𝜑 ∨ 𝜓) → 𝜓) | ||
| Theorem | bj-jaoi2 36573 | Shortens consensus 1053 (110>106), elnn0z 12626 (336>329), pm1.2 904 (20>19), pm3.2ni 881 (43>39), pm4.44 999 (55>51). (Contributed by BJ, 30-Sep-2019.) |
| ⊢ (𝜑 → 𝜓) ⇒ ⊢ ((𝜓 ∨ 𝜑) → 𝜓) | ||
A few other characterizations of the biconditional. The inter-definability of logical connectives offers many ways to express a given statement. Some useful theorems in this regard are df-or 849, df-an 396, pm4.64 850, imor 854, pm4.62 857 through pm4.67 398, and, for the De Morgan laws, ianor 984 through pm4.57 993. | ||
| Theorem | bj-dfbi4 36574 | Alternate definition of the biconditional. (Contributed by BJ, 4-Oct-2019.) |
| ⊢ ((𝜑 ↔ 𝜓) ↔ ((𝜑 ∧ 𝜓) ∨ ¬ (𝜑 ∨ 𝜓))) | ||
| Theorem | bj-dfbi5 36575 | Alternate definition of the biconditional. (Contributed by BJ, 4-Oct-2019.) |
| ⊢ ((𝜑 ↔ 𝜓) ↔ ((𝜑 ∨ 𝜓) → (𝜑 ∧ 𝜓))) | ||
| Theorem | bj-dfbi6 36576 | Alternate definition of the biconditional. (Contributed by BJ, 4-Oct-2019.) |
| ⊢ ((𝜑 ↔ 𝜓) ↔ ((𝜑 ∨ 𝜓) ↔ (𝜑 ∧ 𝜓))) | ||
| Theorem | bj-bijust0ALT 36577 | Alternate proof of bijust0 204; shorter but using additional intermediate results. (Contributed by NM, 11-May-1999.) (Proof shortened by Josh Purinton, 29-Dec-2000.) (Revised by BJ, 19-Mar-2020.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ¬ ((𝜑 → 𝜑) → ¬ (𝜑 → 𝜑)) | ||
| Theorem | bj-bijust00 36578 | A self-implication does not imply the negation of a self-implication. Most general theorem of which bijust 205 is an instance (bijust0 204 and bj-bijust0ALT 36577 are therefore also instances of it). (Contributed by BJ, 7-Sep-2022.) |
| ⊢ ¬ ((𝜑 → 𝜑) → ¬ (𝜓 → 𝜓)) | ||
| Theorem | bj-consensus 36579 | Version of consensus 1053 expressed using the conditional operator. (Remark: it may be better to express it as consensus 1053, using only binary connectives, and hinting at the fact that it is a Boolean algebra identity, like the absorption identities.) (Contributed by BJ, 30-Sep-2019.) |
| ⊢ ((if-(𝜑, 𝜓, 𝜒) ∨ (𝜓 ∧ 𝜒)) ↔ if-(𝜑, 𝜓, 𝜒)) | ||
| Theorem | bj-consensusALT 36580 | Alternate proof of bj-consensus 36579. (Contributed by BJ, 30-Sep-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((if-(𝜑, 𝜓, 𝜒) ∨ (𝜓 ∧ 𝜒)) ↔ if-(𝜑, 𝜓, 𝜒)) | ||
| Theorem | bj-df-ifc 36581* | Candidate definition for the conditional operator for classes. This is in line with the definition of a class as the extension of a predicate in df-clab 2715. We reprove the current df-if 4526 from it in bj-dfif 36582. (Contributed by BJ, 20-Sep-2019.) (Proof modification is discouraged.) |
| ⊢ if(𝜑, 𝐴, 𝐵) = {𝑥 ∣ if-(𝜑, 𝑥 ∈ 𝐴, 𝑥 ∈ 𝐵)} | ||
| Theorem | bj-dfif 36582* | Alternate definition of the conditional operator for classes, which used to be the main definition. (Contributed by BJ, 26-Dec-2023.) (Proof modification is discouraged.) |
| ⊢ if(𝜑, 𝐴, 𝐵) = {𝑥 ∣ ((𝜑 ∧ 𝑥 ∈ 𝐴) ∨ (¬ 𝜑 ∧ 𝑥 ∈ 𝐵))} | ||
| Theorem | bj-ififc 36583 | A biconditional connecting the conditional operator for propositions and the conditional operator for classes. Note that there is no sethood hypothesis on 𝑋: it is implied by either side. (Contributed by BJ, 24-Sep-2019.) Generalize statement from setvar 𝑥 to class 𝑋. (Revised by BJ, 26-Dec-2023.) |
| ⊢ (𝑋 ∈ if(𝜑, 𝐴, 𝐵) ↔ if-(𝜑, 𝑋 ∈ 𝐴, 𝑋 ∈ 𝐵)) | ||
Miscellaneous theorems of propositional calculus. | ||
| Theorem | bj-imbi12 36584 | Uncurried (imported) form of imbi12 346. (Contributed by BJ, 6-May-2019.) |
| ⊢ (((𝜑 ↔ 𝜓) ∧ (𝜒 ↔ 𝜃)) → ((𝜑 → 𝜒) ↔ (𝜓 → 𝜃))) | ||
| Theorem | bj-falor 36585 | Dual of truan 1551 (which has biconditional reversed). (Contributed by BJ, 26-Oct-2019.) (Proof modification is discouraged.) |
| ⊢ (𝜑 ↔ (⊥ ∨ 𝜑)) | ||
| Theorem | bj-falor2 36586 | Dual of truan 1551. (Contributed by BJ, 26-Oct-2019.) (Proof modification is discouraged.) |
| ⊢ ((⊥ ∨ 𝜑) ↔ 𝜑) | ||
| Theorem | bj-bibibi 36587 | A property of the biconditional. (Contributed by BJ, 26-Oct-2019.) (Proof modification is discouraged.) |
| ⊢ (𝜑 ↔ (𝜓 ↔ (𝜑 ↔ 𝜓))) | ||
| Theorem | bj-imn3ani 36588 | Duplication of bnj1224 34815. Three-fold version of imnani 400. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.) (Revised by BJ, 22-Oct-2019.) (Proof modification is discouraged.) |
| ⊢ ¬ (𝜑 ∧ 𝜓 ∧ 𝜒) ⇒ ⊢ ((𝜑 ∧ 𝜓) → ¬ 𝜒) | ||
| Theorem | bj-andnotim 36589 | Two ways of expressing a certain ternary connective. Note the respective positions of the three formulas on each side of the biconditional. (Contributed by BJ, 6-Oct-2018.) |
| ⊢ (((𝜑 ∧ ¬ 𝜓) → 𝜒) ↔ ((𝜑 → 𝜓) ∨ 𝜒)) | ||
| Theorem | bj-bi3ant 36590 | This used to be in the main part. (Contributed by Wolf Lammen, 14-May-2013.) (Revised by BJ, 14-Jun-2019.) |
| ⊢ (𝜑 → (𝜓 → 𝜒)) ⇒ ⊢ (((𝜃 → 𝜏) → 𝜑) → (((𝜏 → 𝜃) → 𝜓) → ((𝜃 ↔ 𝜏) → 𝜒))) | ||
| Theorem | bj-bisym 36591 | This used to be in the main part. (Contributed by Wolf Lammen, 14-May-2013.) (Revised by BJ, 14-Jun-2019.) |
| ⊢ (((𝜑 → 𝜓) → (𝜒 → 𝜃)) → (((𝜓 → 𝜑) → (𝜃 → 𝜒)) → ((𝜑 ↔ 𝜓) → (𝜒 ↔ 𝜃)))) | ||
| Theorem | bj-bixor 36592 | Equivalence of two ternary operations. Note the identical order and parenthesizing of the three arguments in both expressions. (Contributed by BJ, 31-Dec-2023.) |
| ⊢ ((𝜑 ↔ (𝜓 ⊻ 𝜒)) ↔ (𝜑 ⊻ (𝜓 ↔ 𝜒))) | ||
In this section, we prove some theorems related to modal logic. For modal logic, we refer to https://en.wikipedia.org/wiki/Kripke_semantics, https://en.wikipedia.org/wiki/Modal_logic and https://plato.stanford.edu/entries/logic-modal/. Monadic first-order logic (i.e., with quantification over only one variable) is bi-interpretable with modal logic, by mapping ∀𝑥 to "necessity" (generally denoted by a box) and ∃𝑥 to "possibility" (generally denoted by a diamond). Therefore, we use these quantifiers so as not to introduce new symbols. (To be strictly within modal logic, we should add disjoint variable conditions between 𝑥 and any other metavariables appearing in the statements.) For instance, ax-gen 1795 corresponds to the necessitation rule of modal logic, and ax-4 1809 corresponds to the distributivity axiom (K) of modal logic, also called the Kripke scheme. Modal logics satisfying these rule and axiom are called "normal modal logics", of which the most important modal logics are. The minimal normal modal logic is also denoted by (K). Here are a few normal modal logics with their axiomatizations (on top of (K)): (K) axiomatized by no supplementary axioms; (T) axiomatized by the axiom T; (K4) axiomatized by the axiom 4; (S4) axiomatized by the axioms T,4; (S5) axiomatized by the axioms T,5 or D,B,4; (GL) axiomatized by the axiom GL. The last one, called Gödel–Löb logic or provability logic, is important because it describes exactly the properties of provability in Peano arithmetic, as proved by Robert Solovay. See for instance https://plato.stanford.edu/entries/logic-provability/ 1809. A basic result in this logic is bj-gl4 36596. | ||
| Theorem | bj-axdd2 36593 | This implication, proved using only ax-gen 1795 and ax-4 1809 on top of propositional calculus (hence holding, up to the standard interpretation, in any normal modal logic), shows that the axiom scheme ⊢ ∃𝑥⊤ implies the axiom scheme ⊢ (∀𝑥𝜑 → ∃𝑥𝜑). These correspond to the modal axiom (D), and in predicate calculus, they assert that the universe of discourse is nonempty. For the converse, see bj-axd2d 36594. (Contributed by BJ, 16-May-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ (∃𝑥𝜑 → (∀𝑥𝜓 → ∃𝑥𝜓)) | ||
| Theorem | bj-axd2d 36594 | This implication, proved using only ax-gen 1795 on top of propositional calculus (hence holding, up to the standard interpretation, in any modal logic), shows that the axiom scheme ⊢ (∀𝑥𝜑 → ∃𝑥𝜑) implies the axiom scheme ⊢ ∃𝑥⊤. These correspond to the modal axiom (D), and in predicate calculus, they assert that the universe of discourse is nonempty. For the converse, see bj-axdd2 36593. (Contributed by BJ, 16-May-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((∀𝑥⊤ → ∃𝑥⊤) → ∃𝑥⊤) | ||
| Theorem | bj-axtd 36595 | This implication, proved from propositional calculus only (hence holding, up to the standard interpretation, in any modal logic), shows that the axiom scheme ⊢ (∀𝑥𝜑 → 𝜑) (modal T) implies the axiom scheme ⊢ (∀𝑥𝜑 → ∃𝑥𝜑) (modal D). See also bj-axdd2 36593 and bj-axd2d 36594. (Contributed by BJ, 16-May-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((∀𝑥 ¬ 𝜑 → ¬ 𝜑) → ((∀𝑥𝜑 → 𝜑) → (∀𝑥𝜑 → ∃𝑥𝜑))) | ||
| Theorem | bj-gl4 36596 | In a normal modal logic, the modal axiom GL implies the modal axiom (4). Translated to first-order logic, Axiom GL reads ⊢ (∀𝑥(∀𝑥𝜑 → 𝜑) → ∀𝑥𝜑). Note that the antecedent of bj-gl4 36596 is an instance of the axiom GL, with 𝜑 replaced by (∀𝑥𝜑 ∧ 𝜑), which is a modality sometimes called the "strong necessity" of 𝜑. (Contributed by BJ, 12-Dec-2019.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((∀𝑥(∀𝑥(∀𝑥𝜑 ∧ 𝜑) → (∀𝑥𝜑 ∧ 𝜑)) → ∀𝑥(∀𝑥𝜑 ∧ 𝜑)) → (∀𝑥𝜑 → ∀𝑥∀𝑥𝜑)) | ||
| Theorem | bj-axc4 36597 | Over minimal calculus, the modal axiom (4) (hba1 2293) and the modal axiom (K) (ax-4 1809) together imply axc4 2321. (Contributed by BJ, 29-Nov-2020.) (Proof modification is discouraged.) (New usage is discouraged.) |
| ⊢ ((∀𝑥𝜑 → ∀𝑥∀𝑥𝜑) → ((∀𝑥(∀𝑥𝜑 → 𝜓) → (∀𝑥∀𝑥𝜑 → ∀𝑥𝜓)) → (∀𝑥(∀𝑥𝜑 → 𝜓) → (∀𝑥𝜑 → ∀𝑥𝜓)))) | ||
In this section, we assume that, on top of propositional calculus, there is given a provability predicate Prv satisfying the three axioms ax-prv1 36599 and ax-prv2 36600 and ax-prv3 36601. Note the similarity with ax-gen 1795, ax-4 1809 and hba1 2293 respectively. These three properties of Prv are often called the Hilbert–Bernays–Löb derivability conditions, or the Hilbert–Bernays provability conditions. This corresponds to the modal logic (K4) (see previous section for modal logic). The interpretation of provability logic is the following: we are given a background first-order theory T, the wff Prv 𝜑 means "𝜑 is provable in T", and the turnstile ⊢ indicates provability in T. Beware that "provability logic" often means (K) augmented with the Gödel–Löb axiom GL, which we do not assume here (at least for the moment). See for instance https://plato.stanford.edu/entries/logic-provability/ 2293. Provability logic is worth studying because whenever T is a first-order theory containing Robinson arithmetic (a fragment of Peano arithmetic), one can prove (using Gödel numbering, and in the much weaker primitive recursive arithmetic) that there exists in T a provability predicate Prv satisfying the above three axioms. (We do not construct this predicate in this section; this is still a project.) The main theorems of this section are the "easy parts" of the proofs of Gödel's second incompleteness theorem (bj-babygodel 36604) and Löb's theorem (bj-babylob 36605). See the comments of these theorems for details. | ||
| Syntax | cprvb 36598 | Syntax for the provability predicate. |
| wff Prv 𝜑 | ||
| Axiom | ax-prv1 36599 | First property of three of the provability predicate. (Contributed by BJ, 3-Apr-2019.) |
| ⊢ 𝜑 ⇒ ⊢ Prv 𝜑 | ||
| Axiom | ax-prv2 36600 | Second property of three of the provability predicate. (Contributed by BJ, 3-Apr-2019.) |
| ⊢ (Prv (𝜑 → 𝜓) → (Prv 𝜑 → Prv 𝜓)) | ||
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