382 Length of Day Revisited The length of a day depends on the day of the year as well as on the latitude of the location. Latitude gives the location of a point on Earth north or south of the equator. In Chapter 4 we found a model that describes the relation between the length of day and latitude for a specific day of the year. In the Internet Project at the end of this chapter, we will find a model that describes the relation between the length of day and day of the year for a specific latitude. —See the Internet-based Chapter Project— A Look Back In Chapter 2, we began our discussion of functions. We defined domain and range and independent and dependent variables; we found the value of a function and graphed functions. We continued our study of functions by listing properties of functions, such as being even or odd, and we created a library of functions, naming key functions and listing their properties, including the graph. In Chapter 5, we introduced exponential and logarithmic functions, which we classified as transcendental functions. A Look Ahead In this chapter, we continue to study transcendental functions by defining the trigonometric functions, six functions that have wide application. We find their domain and range, evaluate them, graph them, and develop a list of their properties. There are two widely accepted approaches to the development of the trigonometric functions: one uses right triangles; the other uses circles, especially the unit circle. In this text, we develop the trigonometric functions using the unit circle. In Chapter 8, we present right triangle trigonometry. Outline 6. 1 Angles, Arc Length, and Circular Motion 6. 2 Trigonometric Functions: Unit Circle Approach 6. 3 Properties of the Trigonometric Functions 6. 4 Graphs of the Sine and Cosine Functions 6. 5 Graphs of the Tangent, Cotangent, Cosecant, and Secant Functions 6. 6 Phase Shift; Sinusoidal Curve Fitting Chapter Review Chapter Test Cumulative Review Chapter Project Trigonometric Functions 6 Credit: Skylines/Shutterstock
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