A trigonometric model is used when the data seems to follow a cyclical pattern, repeating over time. Examples of this are the height of the sun in the sky, or changes in temperature over the course of a day. When you want to model your data with trigonometric functions, use one of the formulas below.

These formulas for the rest of the coefficients apply to both the sine and cosine functions:

$$\begin{array}{llll}\hfill d& =\frac{y_{\max }+y_{\min }}{2}& \hfill & \\ \hfill A& =\frac{y_{\max }-y_{\min }}{2}& \hfill & \\ \hfill c& =\frac{2\pi }{P}& \hfill & \end{array}$$