Question

Make cos C the subject of the formula C?= a? + b? - 2ab cos C

Answer 1

Answer:  Choice E

Work Shown:

$c^2 = a^2 + b^2 - 2ab\cos(C)\\\\c^2 + 2ab\cos(C) = a^2 + b^2\\\\2ab\cos(C) = a^2 + b^2 - c^2\\\\\boldsymbol{\cos(C) = \frac{a^2 + b^2 - c^2}{2ab}}$