How to Graph a Function in Excel. A mathematical function is a formula that takes an input, x, applies a set of calculations to it, and produces an output called y.

A sine wave is an S-shaped waveform defined by the mathematical function y = sin x. It is depicted graphically as two semi-circular curves that alternate above and below a center line.

However, it's still hard to get an intuitive sense of the relationship between the circle and the trigonometric functions and the triangles. That all changes with animated GIFs. Change over time ...