1. Class Work 1.Sketch a right triangle that has acute angle , and find the five other trig ratios of . 2.Evaluate the expression without using a calculator.

2. Class Work 3. Solve the triangle.

3. Section 6.5 Law of Cosines Objectives: Use the Law of Cosines to solve triangles. Use Heron’s Formula to find the area of a triangle.

4. Law of Cosines:

5. If you need to solve for an angle you will want to use these formulas instead.

6. Ex 1. Solve the triangle. B A C 5 8 12

7. Ex 2. Solve the triangle. A B C 39 63 76

8. Class Work 4. Use the Law of Cosines to solve for .

9. Ex 3. Solve  ABC given  A=25 , b = 10, c = 20

10. EX 4. Solve for x.

11. Class Work 5. Solve for x.

12. 6. Solve  ABC given b = 60, c = 30,  A=70 .

13. 7. Determine whether you need to use the Law of Sines or the Law of Cosines to solve. Then find either x or . a) b) c) d)

14. Heron’s Formula:

15. Ex 5. Find the area of the triangle with sides a =15, b = 23, c = 16.

16. Class Work 8. Find the area of the triangle with sides a = 50, b = 17, c = 41.

17. HW #4 P513 2,3,5,8,9,12,19-22all,27,28