Table of Contents### The Heart of Trig

#### Sine, Cosine, and Tangent

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Is it all coming back to you yet? I hope so, because here's where we get to the real inner workings of trigonometry—where you can see how it's all going to come together. In this section we will cover the sine, cosine, and tangent functions, as well as projection. With knowledge of these operations under your belt, you will be able to understand the programming concepts you'll encounter in the following chapters (especially Chapter 6, “Collision Reactions”).

Sine, cosine, and tangent are known as trigonometric functions. Although what they mean is very simple, many people have trouble understanding them. This conceptual problem happens because it is easy to think that the trigonometric functions give a result by some esoteric or even mystical process. The truth is that these functions just use various ratios of the triangle side lengths to give results. Look at the triangle in the figure below. Notice that we are using x and y instead of a and b to label the side lengths. These are more common side names in programming. Notice the angle in the figure labeled angle.