Math Primer: Trigonometry 101 - Flash 3D: Animation, Interactivity, and Games - page 116

trigonometry trigon • metry

measuring trigons

Now that's more like it. Trigonometry is all about trigons, or shapes with three sides.
Most of our closest friends like to refer to these shapes as triangles. Trig (let's shorten
the word so it doesn't sound so imposing) has to do with the study of triangles and the
relationship of their sides and angles. Since all triangles have only three sides and three
angles, how bad can it be? Not bad, honestly.

It's true there are a lot of different types of triangles in this world. Figure 5.1 shows a
few of them. Obtuse triangles have an angle greater than 90 degrees. Isosceles trian-
gles have two angles (and two sides) that are the same. Acute triangles all have angles
less than 90 degrees. A special type of triangle, called a right triangle, is one where
one of the angles is equal to 90 degrees and is often indicated with a little square in the
corner of the 90-degree angle. One of the neat things about triangles is that the angles
inside them always add up to 180 degrees. Most of trig, and certainly the topics we'll be
covering in this chapter, have to do with right triangles.

Obtuse Isosceles Acute Right

Figure 5.1 Different types of triangles

Coordinate Systems

Coordinate systems provide a way of laying out and measuring space. Probably the
most common are Cartesian coordinate systems, named after the French mathemati-
cian and philosopher Rene Descartes (“I think, therefore I am”). If you have ever used
a grid, you are already familiar with them. A Cartesian coordinate system is simply a
set of equally spaced horizontal and vertical lines (a grid), with a horizontal axis called
the x-axis and a vertical axis called the y-axis. The left graphic in Figure 5.2 shows a
standard coordinate system. The monitor screen provides a convenient place for such
a coordinate system, and we will refer to these as the screen coordinates.