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Chapter 1. Reasoning in Geometry. Section 1-1. Patterns and inductive reasoning. Inductive Reasoning. When you make a conclusion based on a pattern of examples or past events. Conjecture. A conclusion that you reach based on inductive reasoning. Counterexample.
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Chapter 1 Reasoning in Geometry
Section 1-1 Patterns and inductive reasoning
Inductive Reasoning When you make a conclusion based on a pattern of examples or past events
Conjecture A conclusion that you reach based on inductive reasoning
Counterexample An example that shows your conjecture is false It only takes one counterexample to prove your conjecture false
Examples Find the next three terms of each sequence. 11.2, 9.2, 7.2, ……. 1, 3, 7, 13, 21, ……. ……..
Section 1-2 Points, lines and planes
Point A basic unit of geometry Has no size Named using capital letters
Line A series of points that extends without end in two directions. Named with a single lowercase letter or by two points on the line
Collinear and Noncollinear Points that lie on the same line Points that do not lie on the same line
Ray Has a definite starting point and extends without end in one direction Starting point is called the endpoint Named using the endpoint first, then another point
Line Segment Has a definite beginning and end Part of a line Named using endpoints
Plane A flat surface that extends without end in all directions Named with a single uppercase script letter or three noncollinear points
Coplanar and Noncoplanar Points that lie in the same plane Points that do not lie in the same plane
Section 1-3 postulates
Postulates Facts about geometry that are accepted as true
Postulate 1-1 Two points determine a unique line
Postulate 1-2 If two distinct lines intersect, then their intersection is a point.
Postulate 1-3 Three noncollinear points determine a unique plane.
Postulate 1-4 If two distinct planes intersect, then their intersection is a line.
Section 1-4 Conditional statements and their converses
Conditional Statement Written in if-then form Examples: Ifpoints are collinear, then they lie on the same line. Ifa figure is a triangle,then it has three angles. If two lines are parallel, then they never intersect.
Hypothesis The part following the if If points are collinear, then they lie on the same line. If a figure is a triangle,then it has three angles. If two lines are parallel, then they never intersect.
Conclusion The part following the then If points are collinear, then they lie on the same line. Ifa figure is a triangle,then it has three angles. If two lines are parallel, thenthey never intersect.
Converse A conditional statement is formed by exchanging the hypothesis and the conclusion in a conditional statement
Example Statement: If a figure is a triangle, then it has three angles. Converse: If a figure has three angles, then it is a triangle.
Section 1-6 A plan for problem solving
Perimeter The distance around a figure
Formula An equation that shows how certain quantities are related
Area The number of square units needed to cover the surface of a figure