## Trigonometry (11th Edition) Clone

$C = 92.2^{\circ}$
We can try to use the law of cosines to find $C$: $c^2 = a^2+b^2-2ab~cos~C$ $2ab~cos~C = a^2+b^2-c^2$ $cos~C = \frac{a^2+b^2-c^2}{2ab}$ $cos~C = \frac{13^2+7^2-15^2}{(2)(13)(7)}$ $cos~C = -0.03846$ $C = arccos(-0.03846)$ $C = 92.2^{\circ}$