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Truth Tables for Negation, Conjunction, and Disjunction
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Use the definitions of negation, conjunction, and disjunction. Construct truth tables. Determine the truth values of a compound statement for a specific case.
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In 2006, USA Today analyzed patterns in the deaths of four- year college students since January 2000. Their most dominant finding was the freshmen emerged as the class most likely to make a fatal mistake. Freshman accounted for more than 1/3 of all undergraduate deaths, even though they made up only 24% of the population enrolled in 4-year institutions. In this section, you will work with 2 circle graphs based on data from the USA Today study. By determining when statements involving negation, ~ (not), conjunction, (and), and disjunction, (or), are true and when they are false, you will be able to draw conclusions from the data. Classifying a statement as true or false is called assigning a truth value to the statement.
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The negation of a true statement is a false statement, and the negation of a false statement is a true statement. We can express this in a table where T represents true and F represents false. p~p TF FT
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A friend tells you, “I visited London and I visited Paris.” In order to understand the truth values for this statement we will break it down into its two simple statements. p: I visited London. q: I visited Paris. There are 4 possible cases to consider.
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4 Cases: A conjunction statement is true only when both simple statements are true. pqp q TTT TFF FTF FFF
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Now your friend states, “I will visit London or I will visit Paris.” p: I will visit London. q: I will visit Paris. There are 4 possible cases here to consider also.
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4 Cases: A disjunction statement is false only when both component statements are false. pqp q TTT TFT FTT FFF
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If you learn the truth table for and and or by remembering the one different line in each table, it will help you do logic calculations more quickly.
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Determine the truth value for each statement. p: 4 + 6 = 10 q: 5 X 8 = 80 ~p
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Determine the truth value for each statement. p: 4 + 6 = 10 q: 5 X 8 = 80 q p
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Determine the truth value for each statement. p: 4 + 6 = 10 q: 5 X 8 = 80 p ~q
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Determine the truth value for each statement. p: 4 + 6 = 10 q: 5 X 8 = 80 ~q ~p
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If p represents a true statement and q represents a false statement, what is the truth value of each statement? p q
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If p represents a true statement and q represents a false statement, what is the truth value of each statement? p q
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If p represents a true statement and q represents a false statement, what is the truth value of each statement? (~p) q
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If p represents a true statement and q represents a false statement, what is the truth value of each statement? ~(p ~q)
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Use numbers to specify the order in which you would perform the logical operations for each statement. (~p q) ~p
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Use numbers to specify the order in which you would perform the logical operations for each statement. p ~ (q ~p) ~q
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Classwork: TB pg. 98/1 – 12 All ▪ Remember you must write the problems and show ALL work to receive credit for the assignment.
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Section 2.3 Continued
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Construct a truth table. (~p) q
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Construct a truth table. ~(p ~q)
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Construct a truth table. (p q) ~p
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Construct a truth table. (p ~q) (~p q)
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Construct a truth table. (p ~q) (~p q)
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Some truth tables have 3 simple statements. In this situation, you would have 8 cases. pqr TTT TTF TFT TFF FTT FTF FFT FFF
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p (~q r)
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~(p q) ~r
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~(p ~q) ~r
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Logically Equivalent – two statements that have the same variable, and when their truth tables are computed, the final columns are identical.
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Determine if the two compound statements are logically equivalent. ~(p ~q) ~ (p q) p (p q)
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Determine if the two compound statements are logically equivalent. ~(p ~q) ~ (p q) (~p q) (~p ~q)
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Classwork: TB pg. 98/30 – 40 Even, and 60 – 66 Even ▪ Remember you must write the problem and show ALL work to receive credit for this assignment. ▪ NOTE: If your truth tables are not complete, then your answer is wrong.
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