4th Grade Math - Angles Lesson
An angle is formed by the intersection of two line segments, rays, and/or lines.
The point of intersection is referred to as the vertex.
The amount of turn between the two line segments,
rays, and/or lines of an angle is the measure of the angle.
Angles are typically measured in degrees or radians.
Angle measure is based on a circle where a full turn around the circle is 360 degrees.
Similarly, a half turn is 180 degrees, a fourth [quarter] turn is 90 degrees, and so on.
A 180° angle is sometimes referred to as a straight angle.
A 90° angle is referred to as a right angle.