Chapter 1: Q1RE (page 111)
a) Define the negation of a proposition.
b) What is the negation of “This is a boring course”?
(a) The negation of a proposition is the opposite of the given mathematical proposition.
(b) The negation of “This is a boring course” is “This is not a boring course”.
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A says “We are both knaves” and B says nothing. Exercises 24–31 relate to inhabitants of an island on which there are three kinds of people: knights who always tell the truth, knaves who always lie, and spies (called normals by Sullying [Sm78]) who can either lie or tell the truth. You encounter three people, A, B, and C. You know one of these people is a knight, one is a knave, and one is a spy. Each of the three people knows the type of person each of other two is. For each of these situations, if possible, determine whether there is a unique solution and determine who the knave, knight, and spy are. When there is no unique solution, list all possible solutions or state that there are no solutions
A says “I am the knight,” B says “I am the knight,” and C says “I am the knight.”
Use De Morgan’s laws to find the negation of each of the following statements.
(a) Kewame will take a job in industry or go to graduate school.
(b) Yoshiko knows Java and calculus.
(c) James is young and strong.
(d) Rita will move to Oregon or Washington.
Write each of these propositions in the form “p if and only if q” in English.
a) If it is hot outside you buy an ice cream cone, and if you buy an ice cream cone it is hot outside.
b) For you to win the contest it is necessary and sufficient that you have the only winning ticket.
c) You get promoted only if you have connections, and you have connections only if you get promoted.
d) If you watch television your mind will decay, and conversely.
e) The trains run late on exactly those days when I take it.
A says “The two of us are both knights” and B says A “ is a knave.”
Let p, q, and r be the propositions p : You get an A on the final exam. q : You do every exercise in this book. r : You get an A in this class. Write these propositions using p, q, and r and logical connectives (including negations).
a)You get an A in this class, but you do not do every exercise in this book.
b) You get an A on the final, you do every exercise in this book, and you get an A in this class.
c) To get an A in this class, it is necessary for you to get an A on the final.
d) You get an A on the final, but you don’t do every exercise in this book; nevertheless, you get an A in this class.
e) Getting an A on the final and doing every exercise in this book is sufficient for getting an A in this class.
f ) You will get an A in this class if and only if you either do every exercise in this book or you get an A on the final.
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