Question

HELP!! TRIG LAW OF COSINES

Determine the approximate measure of angle C.

90.0 degrees

95.7 degrees

60.9 degrees

102.3 degrees

Answer 1

C ≈ 95.7°

Explanation:

Law of cosines:

c² = a² + b² − 2ab cos C

where a, b, and c are the sides of the triangle, and C is the angle opposite of side c.

9² = 5² + 7² − 2(5)(7) cos C

81 = 25 + 49 − 70 cos C

81 = 25 + 49 − 70 cos C

7 = -70 cos C

-1/10 = cos C

C ≈ 95.7°