Trigonometry For Dummies, 2nd Edition

Chapter 9

Defining Trig Functions Globally

In This Chapter

Assigning trig function values from the unit circle

Using reference angles and terminal sides

Using coordinates to calculate trig functions

Defining trig-function domains and ranges

The six basic trig functions all had humble beginnings with the right triangle and its angles. The unit circle opens up a whole new world for the input values into those functions. Because of the nature of trig functions — they repeat the same patterns over and over — the output values show up regularly. This repetition is a good thing; you recognize where in the pattern a particular input belongs and then assign the output. Life is good.

Defining Trig Functions for All Angles

So many angles are used in trigonometry and other math areas, and the majority of those angles are multiples of 30 and 45 degrees. So, having a trick up your sleeve letting you quickly access the function values of this frequent-flier list of angles makes perfect sense. All you need to know or memorize are the values of the trig functions for 0-, 30-, 45-, 60-, and 90-degree ...