Note that C-B is considered the hypotenuse of the of traingle. Therefore, according to the acronym SOH CAH TOA, Cos C = Adjacent/ Hypotenuse, where the adjacent is 8√34 and the hypotenuse is given by by pythagoreas theorem (a²+b² = c²) or c=√(a²+b²) → c=√4352
Then Cos C = (8√34) /(√4352) → this simplifies into √2 on the top and 2 on the bottom once we simplify.
Final Answer: