2. Aim: What is the Law of Sine? Do Now: In ∆ABC, AC = b, BC = a, and the height is (h). Find: 1. sin A 2. sin B A D B C HW: p.567 # 6,8,12,19,20,21,22,23

3. We can use the same idea to find and

4. Law of Sine Use any of the two ratios, we can form a proportion and solve one unknown value.

5. When do we use Law of Sine to solve problems? AAS ASA SSA The letters stand for the known values of sides and angles Notice that if we only know the measurements of three angles of a triangle. Neither Law of Sine nor Law of Cosine can be used to solve the problem. In other words, AAA is not good for either Law

6. In the accompanying diagram of a streetlight, the light is attached to a pole at R and supported by a brace, feet, is an obtuse angle, and Find the length of the brace, to the nearest foot.

7. Application: 1. In ∆ABC, a = 10, and Find b to the nearest integer. 2. In ∆ABC, and c = 10. Find a to the nearest tenths.,

8. 3. In ∆ABC, a = 12, sin A = 1/3, sin C = 1/4. Find c. (c = 9) 4. In ∆ABC, a = 20, b = 16 and m  B = 25 . Find  C to the nearest degree. 5. Points A and B are on opposite sides of a lunar crater. Point C is 50m from A. If m  A = 112° and m  C = 42° what is the width of the crater? (  C = 123°) (82m)