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Class Work 1. Sketch a right triangle that has acute angle , and find the five other trig ratios of . 7 cos in quad IV 25 2. Evaluate the expression without using a calculator. sin cos 4 4 2 2 Class Work 3. Solve the triangle. 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. Law of Cosines: If you need to solve for an angle you will want to use these formulas instead. b2 c2 a 2 cos A 2bc a 2 c2 b2 cos B 2ac 2 2 2 a b c cos C 2ab Ex 1. Solve the triangle. C 5 8 A 12 B Ex 2. Solve the triangle. C 76 39 A 63 B Class Work 4. Use the Law of Cosines to solve for . Ex 3. Solve ABC given A=25, b = 10, c = 20 EX 4. Solve for x. Class Work 5. Solve for x. 6. Solve ABC given b = 60, c = 30, A=70. 7. Determine whether you need to use the Law of Sines or the Law of Cosines to solve. Then find either x or . a) d) b) c) Heron’s Formula: Ex 5. Find the area of the triangle with sides a =15, b = 23, c = 16. Class Work 8. Find the area of the triangle with sides a = 50, b = 17, c = 41. HW #4 P513 2,3,5,8,9,12,19-22all,27,28