### Home > INT3 > Chapter 8 > Lesson 8.3.1 > Problem8-105

8-105.

For $ΔABC$, determine $m∠C$ given that $BC = 30, AC = 15$, and $AB = 21$.

Use the Law of Cosines:
$c^{2} = a^{2} + b^{2} − 2ab\left(\text{cos}C\right)$

$m∠C ≈ 40.5^\circ$