Below you can find a picture with the formulas for all six of them. We define trigonometric functions as ratios between a right triangle's sides.
We focused on that topic in our trigonometry calculator. This observation is, more or less, the idea behind trigonometry: to somehow relate a triangle's inside angles to its sides. After all, if we increase one of the acute angles, we can easily see that the opposite side will have to get longer too. Moreover, we can observe some other dependencies that make the triangle look the way it does. One of their angles is always 90 ° 90\degree 90° (hence, the name), so we already have some information about our shape even before we draw it.
We, however, are most interested in a particular type of triangle: right triangles (you know, the ones that the Pythagorean theorem is all about). In some sense, there can be no simpler polygon. And in geometry, we can't go more basic than triangles: three sides, three vertices, three inside angles. Before we see what a cofunction is, we need to start with the basics.
