Trigonometry, as its Greek and Latin roots suggest, is primarily the study of triangles. As we will see, circles also play a very prominent role. Trigonometric functions are, in fact, sometimes designated as circular functions. Figure 4.1 suggests how a clever caveman might determine the height y of a cliff by measuring the distance x to its base and the angle that he has to look upward. This could be done by making a scale drawing but, more elegantly, using trigonometry, the height y is equal to .
Figure 4.1 Stone-age trigonometry.
In this section we review some ...