Question

ΔABC has three sides with these lengths: AB = 9, BC = 40, and CA = 41. What is the value of cos C?

Answer 1

c=40/41

Explanation:

corect for plato

Answer 2

From the Law of Cosines
Cos (C) = (a^2 + b^2 -c^2) / 2 * a * b
Cos (C) =(40^2 + 41^2 -9^2) / 2 * 40 * 41
Cos (C) = 1,600 + 1,681 - 81 / 3,280
Cos (C) = 3,200 / 3,280
Cos (C) = 0.9756097561
Incidentally, Angle C = 12.68 Degrees