Question

Triangle ABC has three sides with these lengths: AB = 9, BC = 40, and CA = 41. What is the value of cos C? A. 9/41 B. 40/9 C. 40/41 D. 9/40

Answer 1

It's a rectangular triangle because:

9² + 40² = 41²
81 + 1600 = 1681
1681 = 1681

Answer: C. cos∡C = 40/41

Answer 2

The answer is letter C which is 40/41. If you draw a triangle the sides found in the cos C is BC which is equal to 40 and the CA which is equal to 41 or the 40/41. It can not be the AB since it is in the opposite side of the cos C.