Chapter 5 Analytic Trigonometry 1

5.4 Sum & Difference Formulas Objectives:  Use sum and difference formulas to evaluate trigonometric functions, verify identities, and solve trigonometric equations. 2

Consider This….  Determine whether each equation is true or false. Justify your answer. 3

Sum & Difference Formulas  Sine  Cosine 4 Signs are the same. Signs change.

Sum & Difference Formulas  Tangent 5

Example 1  Find the exact value of cos 75 °. Check your answer with a calculator. 6

Example 2  Find the exact value of. 7

Example 3  Simplify. 8

Example 4  Find the exact value of sin (u + v) given where and where 9

Example 5  Prove the cofunction identity. 10

Example 6  Simplify each expression. 11

Example 7  Find all solutions of the equation in the interval [0, 2π). 12

Homework 5.4  Worksheet