ABSTRACT
Trigonometry started life as the study of triangles, but it is now much broader: the study of just about anything to do with either quantitative aspects of angles or processes that repeat at regular intervals. To understand the basic trigonometric functions the readers first need to know some basic geometry to do with circles, angles, and simple shapes made up of straight lines. After introducing these functions, the readers can return to oscillations and waves and the reasons why the trigonometric functions can be used to describe them. The basic functions of trigonometry are the sine, the cosine, and the tangent functions of an angle. In science, these same functions describe at least approximately the oscillations of objects such as atoms in a molecule, the propagation of the sound and light waves, and the hours of the daylight throughout the year.
