1. Jose M Bravo Jr. Chapter 11.1 Introduction to Basic Geometry Basic Geometric Concepts

2. Point, Line, Line Segment Definitions A point is an exact location in space. A point has no dimensions. A line is a collection of points along a straight path that extends endlessly in both directions. A line segment is a part of a line having two endpoints. A line segment has only one dimension-its length. (Example AB on the figure above.) A B

3. Ray, Angle, and Plane A ray is a part of a line having only one endpoint. An angle consists of two rays that have a common endpoint called the vertex of the angle. A plane is a flat surface that extends endlessly in all directions. B A C Vertex

4. Definitions A straight angle is 180 Example A right is an angle That measures 90 An acute angle is less than 90 An obtuse angle is more than 90 and less than 180 Angles are measured in degrees ( ) Angles are classified according to their measures. B A C E F D Y Z X D E C

5. Complementary and Supplementary Angles Complementary angles are two angles whose sum is 90. A 25 B 65 Supplementary angles are two angles whose sum is 180 C 40 D 140

6. Intersecting lines, Parallel lines, Perpendicular lines Intersecting lines are two lines that meet. Parallel lines are two lines in the same plane that do not intersect. Perpendicular lines are two lines that intersect to form right angles. B A DD C E EF GH Symbol for right angle Q T S R P

7. Vertical Angles Vertical angles are two equal angles formed by two intersecting lines. 120 A 60 120 E C D B