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EECS 203-1: Discrete Mathematics Winter 2005 Introductory ...

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Other logical operators and truth tables<br />

• You can take the negation of any proposition, whether or not it is true or<br />

false. The result will be a new proposition with the opposite truth value.<br />

• We express this using a simple display called a truth table.<br />

• The truth table for negation is<br />

p ¬p<br />

T F<br />

F T<br />

• We now introduce two new operators called conjunction and disjunction.<br />

(These are also called “and” and “or”.)<br />

• Examples (relative to today) p is “it is raining today” and q is “today is<br />

Friday”. The proposition “p and q”, notated p ∧ q, is “it is raining today<br />

and today is Friday”. The proposition “p or q, notated p∨q, is “it is raining<br />

today or today is Friday.”<br />

• The truth tables for conjunction and disjunction:<br />

p q p ∧ q<br />

T T T<br />

T F F<br />

F T F<br />

F F F<br />

p q p ∨ q<br />

T T T<br />

T F T<br />

F T T<br />

F F F<br />

6

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