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Pre-Calculus For Dummies, 2nd Edition by Elleyne Kase, Yang Kuang PhD

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Chapter 6

Circling in on Angles

In This Chapter

arrow Discovering alternate trig function definitions

arrow Placing angle measurements on a unit circle

arrow Calculating trig functions on the unit circle

In this chapter, we move on to right triangles drawn on the coordinate plane (x- and y-axes). Moving right triangles onto the coordinate plane brings out many more interesting concepts (such as evaluating trig functions and solving trig equations) that we look at in this chapter, all through a very handy tool known as the unit circle.

The unit circle is extremely important in the real world and in mathematics; for instance, you’re at its mercy whenever you fly in an airplane. Pilots use the unit circle, along with vectors, to fly airplanes in the correct direction and over the correct distance. Imagine the disaster that would result if a pilot tried to land a plane a bit to the left of the runway!

In this chapter, we work on building the unit circle together as we review the basics of angles in radians and triangles. With that information, you can place the triangles onto the unit circle (which is also located in the coordinate plane) to solve the problems we present at the end of this chapter. (We ...

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