MATH145 Lecture Notes - Lecture 4: Propositional Variable, Propositional Calculus
1 Dec 2016
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Document Summary
A class is a collection of sets of the form. {x | f (x ) is true } Where f (x ) is a mathematical statement about an unknown set x . The collection of all sets is the class {x | x = x } If a is a set then a = {x | x a} which is also a class. In the languages of propositional logic we use symbols from the symbol set together with propositional variable symbols such as p, q, r, . The variable symbols are intended to represent mathematical statements which are either true or false. A derivation for a formula f is a list of formulas. 4. 5 example. ( ( p q) (r s)) is a formula and one possible derivation, with justi cation on each line, is as follows: p. 1: q, r, s, p, ( p q, s, r s, ( p q, ( ( p q) (r s))
