In triangle ABCABCABC, sides a=5a = 5a=5, b=6b = 6b=6, c=7c = 7c=7. 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).
frac310\\frac{3}{10}frac310
frac25\\frac{2}{5}frac25
frac210\\frac{2}{10}frac210
frac212\\frac{2}{12}frac212