Now let’s hook up a strip chart recorder to the hypotenuse. We’ll set the pen at the position corresponding to the height of the triangle. When you click the Start button, the hypotenuse will swing around in a circle and leave its trail on the chart recorder.
As you see, it moves in a wavy up-and-down pattern. This pattern is called a sine wave.
We can, of course, hook up another chart recorder to set the pen at the position corresponding to the length of the base of the triangle, and that will show us cosine’s wave form.