Chapter 5. The Unit Circle
So far, we have explored sine and cosine in the context of triangles. You have probably also seen wavy curves representing them, too. How are they related? This chapter begins to discuss how sine and cosine curves are derived from triangles constructed inside a unit circle, which is just a circle of radius equal to 1. As we find out shortly, this also has implications for the trigonometric functions of angles above 90°. When we graph sines and cosines (and other functions) over a range of angles, it results in a curve that repeats itself periodically, called a sinusoid. Let’s tie all these things together!
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