Section 9.6: fix Exercise 9.6.1 statements and add Exercise 9.6.2#488
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rkirov wants to merge 1 commit intoteorth:mainfrom
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Section 9.6: fix Exercise 9.6.1 statements and add Exercise 9.6.2#488rkirov wants to merge 1 commit intoteorth:mainfrom
rkirov wants to merge 1 commit intoteorth:mainfrom
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rkirov
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Apr 19, 2026
rkirov
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- Exercise 9.6.1 c): add parens around the two ¬ ∃ conjuncts (without them, ∧ associates inside the inner ¬ ∃ body, changing the meaning).
- Exercise 9.6.1 b): change domain from (1, 2) to [0, ∞), matching the textbook's unbounded-domain counterexample.
- Split Exercise 9.6.1 docstring labels into a) / b) / c) / d).
- Add Exercise 9.6.2: BddOn.add, BddOn.sub, BddOn.mul, and BddOn.div (the last as a Decidable, since divisibility of the bounded class is the actual question).
- Exercise 9.6.1 c): add parens around the two ¬ ∃ conjuncts (without them, ∧ associates inside the inner ¬ ∃ body, changing the meaning). - Exercise 9.6.1 b): change domain from (1, 2) to [0, ∞), matching the textbook's unbounded-domain counterexample. - Split Exercise 9.6.1 docstring labels into a) / b) / c) / d). - Add Exercise 9.6.2: BddOn.add, BddOn.sub, BddOn.mul, and BddOn.div (the last as a Decidable, since divisibility of the bounded class is the actual question). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
rkirov
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Apr 19, 2026
| example : ∃ f: ℝ → ℝ, BddOn f (.Icc (-1) 1) ∧ | ||
| ¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMinOn f (.Icc (-1) 1) x₀ ∧ | ||
| ¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMaxOn f (.Icc (-1) 1) x₀ | ||
| (¬ ∃ x₀ ∈ Set.Icc (-1) 1, IsMinOn f (.Icc (-1) 1) x₀) ∧ |
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this one was subtle, without parens lean reads it as ¬ (A ∧ ¬ B)
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