Lines and Angles
Lines and Angles
Geometric figures are shapes composed of points, lines, or planes. A point is simply a location in space; it does not have any dimensional properties such as length, area, or volume. Points are written as a single capital letter, such as A or Q.
A collection of points that extends infinitely in both directions is a line. Points that extends infinitely in only one direction is a ray. A section of a line with a beginning and end is a line segment. A line segment is described by the beginning and end points, such as line segment AQ. Lines, rays, and line segments are examples of one-dimensional objects because they can only be measured in one dimension (length).
Lines, rays, and line segments can intersect to create angles, which are measured in degrees or radians. Angles are classified based on the number of degrees.
- Angles between 0° and 90°are acute.
- Angles between 90° and 180° are obtuse.
- An angle of exactly 90° is a right angle.
Two angles with measurements that total to 90° are complementary, and two angles with measurements that total to 180° are supplementary. Two adjacent (touching) angles that are supplementary are called a linear pair.
Two lines that form right angles are perpendicular. Lines that do not intersect are described as parallel.
