Question

The law of cosines a2+b2-2abcosC=c2. Find the value of 2abcosC.

Answer 1

A = 4
B = 3
C = 2

We need to find cos(C)

$4 = 16 + 9 - 2(2)(3)(cos(C))$
$-21 = -12 * cos(C)$
$cos (C)=  1.75$

The answer is $2 * 3 * 4 * 1.75$ = 42