Radian and Degree Measure
As derived from the Greek language, the word Trigonometry means “measurement of triangles”. Initially, trigonometry dealt with relationships among the sides and angles of triangles and was used in the development of astronomy, navigation, and surveying. Nowadays the application of trigonometry expanded to include a vast number of physical phenomena involving rotations and vibrations (sound waves, light rays, planetary orbits, vibrating strings, pendulums…)
An angle is determined by rotating a ray about its endpoint. The starting position of the ray is the initial side of the angle, and the position after rotation is the terminal side. The endpoint of the ray is the vertex of the angle.
This perception of an angle fits a coordinate system in which the origin is the vertex and initial side coincides with the positive x -axis. Such an angle is in standard position. Positive angles are generated by counterclockwise rotation, and negative angles by clockwise rotation.
Find out more about radian and degree measures from the explanation below.
Practice: Describe angles and use the radian and degree measures in the following exercises.