Copyright 2013, 2010, 2007, Pearson, Education, Inc. Section 3.2 Truth Tables for Negation, Conjunction, and Disjunction

Copyright 2013, 2010, 2007, Pearson, Education, Inc. What You Will Learn Truth tables for negations, conjunctions, and disjunctions 3.2-2

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Truth Table A truth table is used to determine when a compound statement is true or false

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Negation Truth Table p~p~p Case 1TF Case 2FT

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Compound Statement Truth Table pq Case 1TT Case 2TF Case 3FT Case 4FF

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Conjunction Truth Table The conjunction is true only when both p and q are true pq p ⋀ q Case 1TTT Case 2TFF Case 3FTF Case 4FFF

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Disjunction Truth Table The disjunction is true when either p is true, q is true, or both p and q are true pq p ⋁ q Case 1TTT Case 2TFT Case 3FTT Case 4FFF

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Negation Negation ~p is read “not p.” If p is true, then ~p is false; if p is false, then ~p is true. In other words, ~p will always have the opposite truth value of p

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Conjunction Conjunction p ⋀ q is read “p and q.” p ⋀ q is true only when both p and q are true 3.2-9

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Disjunction Disjunction p ⋁ q is read “p or q.” p ⋁ q is true when either p is true or q is true, or both p and q are true. In other words, p ⋁ q is false only when both p and q are false

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 1.Determine if the statement is a negation, conjunction, disjunction, conditional, or biconditional. The answer to the truth table appears under: ~ if it is a negation ⋀ if it is a conjunction ⋁ if it is a disjunction → if it is conditional ↔ if it is biconditional

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 2.Complete the columns under the simple statements, p, q, r, and their negations ~p, ~q, ~r, within parentheses, if present. If there are nested parentheses work with the innermost pair first

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 3.Complete the column under the connective within the parentheses, if present. You will use the truth values of the connective in determining the final answer in step

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 4.Complete the column under any remaining statements and their negation

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 5.Complete the column under any remaining connectives. The answer will appear under the column determined in step 1. For a conjunction, disjunction, conditional or biconditional, obtain the value using the last column completed on the left side and on the right side of the connective

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Constructing Truth Tables 5. (continued) For a negation, negate the values of the last column completed within the grouping symbols on the right of the negation. Circle or highlight the answer column and number the columns in the order they were completed

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 3: Truth Table with a Negation Construct a truth table for ~(~q ⋁ p)

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 3: Truth Table with a Negation Construct a truth table for ~(~q ⋁ p). Solution pq~(~q ⋁ p)p) TTFFTTFF TFTFTFTF F F T F F T F T T T F T T T F F False only when p is false and q is true

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Try This Construct a truth table for the following: ~p ^q

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 7: Use the Alternative Method to Construct a Truth Table Construct a truth table for ~p ⋀ ~ q

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 7: Use the Alternative Method to Construct a Truth Table Construct a truth table with four cases. Solution pq TTFFTTFF TFTFTFTF

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 7: Use the Alternative Method to Construct a Truth Table Add a column for ~p ⋀ ~q. Use columns ~p and ~q to find ~p ⋀ ~q. Solution pq TTFFTTFF TFTFTFTF ~p~p ~q~q FFTTFFTT FTFTFTFT ~p ⋀ ~q FFFTFFFT It is true only when ~p and~q are true.

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement Determine the truth value for each simple statement. Then, using these truth values, determine the truth value of the compound statement. 15 is less than or equal to

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement Let p: 15 is less than 9. q: 15 is equal to 9. Express “15 is less than or equal to 9” as p ⋁ q. Both p and q are false. p ⋁ qp ⋁ q F ⋁ F F Solution

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement Determine the truth value for each simple statement. Then, using these truth values, determine the truth value of the compound statement. George Washington was the first U.S. president or Abraham Lincoln was the second U.S. president, but there has not been a U.S. president born in Antarctica

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement Let p: George Washington was the first U.S. president. q: Abraham Lincoln was the second U.S. president. r:There has been a U.S. president who was born in Antarctica. The statement can be written in symbolic form as (p ⋁ q) ⋀ ~r. Solution

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement p: George Washington was the first U.S. president. q: Abraham Lincoln was the second U.S. president. r:There has been a U.S. president who was born in Antarctica. The statement is (p ⋁ q) ⋀ ~r. p is true, q is false, r is false. Since r is false, ~r is true. Solution

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Example 9: Determine the Truth Value of a Compound Statement The statement is (p ⋁ q) ⋀ ~r. p is true, q is false, ~r is true. (p ⋁ q) ⋀ ~r (T ⋁ F) ⋀ T T ⋀ T T The original compound statement is true. Solution

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Try This: P. 117 #

Copyright 2013, 2010, 2007, Pearson, Education, Inc. Homework P. 115 # 6-60 (x3)