In triangle ABCABCABC, sides a=7a = 7a=7, b=8b = 8b=8, c=9c = 9c=9. By the Law of Cosines, c2=a2+b2−2abcos(C)c^2 = a^2 + b^2 - 2ab\\cos(C)c2=a2+b2−2abcos(C). Find cos(C)\\cos(C)cos(C).
frac414\\frac{4}{14}frac414
frac47\\frac{4}{7}frac47
frac514\\frac{5}{14}frac514
frac416\\frac{4}{16}frac416