 Solution

ID: past-exam-of-the-logic-and-set-theory-course-of-the-university-of-oxford/2011/a/1/c/iii/solution

A conjunctive normal form is a finite conjunction of clauses, each clause being a finite disjunction of literals. A literal is a propositional variable or the negation of one. Thus its shape is

i = 1 ⋀ m (j = 1 ⋁ n_{i} ℓ_{ij}), ℓ_{ij} \in {p_{k}, \neg p_{k} : k \in ω} .

A single clause or single literal is allowed; the necessary parentheses can be inserted according to the grammar.

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