Plane Geometry - Bruce E. Shapiro

Plane Geometry - Bruce E. Shapiro Plane Geometry - Bruce E. Shapiro

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24 SECTION 5. LOGIC AND PROOF“I ♥ Geometry!”« CC BY-NC-ND 3.0. Revised: 18 Nov 2012

Section 6The Real NumbersWe will take the terms set and element as undefined terms. We write aset as the list of elements surrounded by curly brackets:or by a rule{A, B, C, ...}{x|S(x)}where S(x) is some rule such as “x is even.”We use x ∈ S to represent “x is an element of the set S.”We denote the natural numbers bythe integers byand the positive integers byN = {1, 2, 3, . . . },Z = {. . . , −3, −2, −1, 0, 1, 2, 3, . . . },Z + = {0, 1, 2, ..}The union of two sets S and T is given byS ∪ T = {x|x ∈ S ∧ x ∈ T }0 This section is intended primarily as a review and hence is necessarily concise.25

Section 6The Real NumbersWe will take the terms set and element as undefined terms. We write aset as the list of elements surrounded by curly brackets:or by a rule{A, B, C, ...}{x|S(x)}where S(x) is some rule such as “x is even.”We use x ∈ S to represent “x is an element of the set S.”We denote the natural numbers bythe integers byand the positive integers byN = {1, 2, 3, . . . },Z = {. . . , −3, −2, −1, 0, 1, 2, 3, . . . },Z + = {0, 1, 2, ..}The union of two sets S and T is given byS ∪ T = {x|x ∈ S ∧ x ∈ T }0 This section is intended primarily as a review and hence is necessarily concise.25

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