To the ancient Greeks, trigonometry was the study of right triangles. Trigonometric functions (sine, cosine, tangent, cotangent, secant, and cosecant) can be defined as right triangle ratios (ratios of the lengths of sides of a right triangle). Thousands of years later, we still find applications of right triangle trigonometry today in sports, surveying, navigation,* and engineering.

*Section 1.5, Example 7 and Exercises 66–68 and 73–74.

IN THIS CHAPTER, we will review angles, degree measure, and special right triangles. We will discuss the properties of similar triangles. We will use the concept of similar right triangles to define the six trigonometric functions as ratios of the lengths of the sides of right triangles (right triangle trigonometry).

LEARNING OBJECTIVES

Understand degree measure.

Learn the conditions that make two triangles similar.

Define the six trigonometric ...

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