1. Lesson 6.5 Law of Cosines

2. Solving a Triangle using Law of Sines 2 The Law of Sines was good for: ASA- two angles and the included side AAS- two angles and any side SSA- two sides and an opposite angle (being aware of possible ambiguity) Why would the Law of Sines not work for an SAS triangle? 15 12.5 26° No side opposite any angle!

3. Law of Cosines: 3

4. Applying the Cosine Law 4 Solve this triangle: 15 12.5 26° A B C c

5. Applying the Cosine Law 5 Now, calculate the angles: Use and solve for B: 15 12.5 26° A B C c = 6.65

6. Applying the Cosine Law 6 Here’s angle A : 180 – 98.48 – 26 = 55.52° 15 12.5 26° A B C c = 6.65 98.48°

7. Wing Span 7 The leading edge of each wing of the B-2 Stealth Bomber measures 105.6 feet in length. The angle between the wing's leading edges is 109.05°. What is the wing span (the distance from A to C)? Answer: 171.99 ft. A C