Oblique Triangles Part II Learning Goal: I can solve for a missing side or angle in a non-right triangle using cosine law

Recall: Sine Law Matching side and angle

Cosine Law We can solve for the third side We can solve for any angle

Example 1 – solving for a side Label the sides of the triangle a, b, and c Calculate the missing side using cosine law 73⁰ 2.3 km 1.9km ? C A B

Example 2 – solving for an angle Label the sides of the triangle x, y, and z Write cosine law for this triangle and calculate angle X 3.3 cm 3.8 cm 2.7 cm Y X Z

Homework Pg # 2,3,7,8

Warm-Up: Cosine Law Label the sides and write triangle Write cosine law to solve for angle M 500 ft 650 ft 750 ft M L N

Applications of Cosine Law Learning Goal: I can solve problems based on realistic situations using cosine law

Example 1 – Navigation Two planes are heading toward a control tower. From the tower, one plane is 86 km due North. The second plane is 146 km away at an angle of 53⁰ W of N. How far apart are the two planes?

Example 2 - Race Course A bike race follows a triangular route. It begins in the town Shaw. Bikers must travel 17km from Shaw to Bronston, 12km from Bronston to Gage, then 19 km back to Shaw. At what angle must the biker turn to continue on the second leg of the race?

Homework Pg. 39 # 10, 11, 13, 15, 18