9.1 Lines and Angles
Chapter 1 / Whole Numbers and Introduction to Algebra Planes A plane is a flat surface that extends indefinitely. Plane Space extends in all directions indefinitely.
Chapter 1 / Whole Numbers and Introduction to Algebra Points The most basic concept of geometry is the idea of a point in space. A point has no length, no width, and no height, but it does have location. We will represent a point by a dot, and we will label points with letters. A Point A
Lines, Segments, and Rays Line AB or AB A B Line Segment AB or AB A B Ray AB or AB A B
Angles An angle is made up of two rays that share the same endpoint called the vertex. A B C x Vertex The angle can be named ABC, CBA, B, or x. The vertex is the middle point.
Chapter 1 / Whole Numbers and Introduction to Algebra Angles An angle can be measured in degrees. There are 360º (degrees) in a full revolution or full circle. 360º
Chapter 1 / Whole Numbers and Introduction to Algebra Classifying Angles Name Angle Measure Examples Acute Angle Between 0° and 90° Right Angle Exactly 90° Obtuse Angle Between 90° and 180° Straight Angle Exactly 180º
Examples For the figure shown, use symbols to name a line, two rays, and a segment. In this figure, XY is 12.3 inches and XZ is 20.1 inches. Find YZ.
Chapter 1 / Whole Numbers and Introduction to Algebra Polygons A polygon is a flat figure formed by line segments connected at their ends. Geometric figures such as triangles, squares, and rectangles are called polygons. triangle square rectangle
Perimeter The perimeter of a polygon is the distance around the polygon.
Example Find the perimeter of this figure. All angles are right angles. Dimensions are in centimeters (cm).