Exercise Notes On Elementary Logic And Quantifiers

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Practice Your Skill 2.2 Write the following in roster form. Set of all fingers Set of all oceans in the world Describe the following sets by its property {1,3,5,7,9} {liquid, gases, solid, plasma} If f(x)=3x+2, find f(2) its inverse. Elementary Logic Logical Connectives A logical connective is the mathematical equivalent of a conjunction. That is, it is a word (or symbol) that joins two sentences to produce a new one. If P and Q are propositions, then P∧Q (conjunction) is the statement that is true if and only if both P and Q are true. Otherwise, P and Q are false. A proposition is a statement that is either true or false but not both. Another connective is the word “or,” and its symbol is "∨". The statement P∨Q (disjunction) …show more content…

2=3≠5 Quantifiers Quantifiers are words that indicate the amount or numbers being referred to. Words such as “all,” “some,”, “every,” “a few” and “nothing” are examples of quantifiers. In English language, there are several quantifiers. However, this leads to some sort of ambiguity. As such, Mathematicians therefore limit to only two quantifiers: the universal quantifier “for all” (or for every) and existential quantifier “there exists” (or for some). In order for us to write complicated mathematical sentences in a highly symbolic form, the symbols ∀ and ∃ are used to denote “for all” and “there exists,” respectively. Example 2.14: Use quantifiers to express the following statements: Every college student needs to take up Mathematics in the Modern World. There is a student in this class who graduated valedictorian. Solution: Let P(x) denote the statement “x needs to take up Mathematics in the Modern World.” The given statement can now be expressed as ∀x P(x) where the domain of discourse consists of the college students. Let Q(x) denote the statement “x who graduated valedictorian.” The given statement can now be expressed as ∃x Q(x) where the domain of discourse consists of students in this

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