Chapter 7 - Applications of Trigonometric Functions - Section 7.3 The Law of Cosines - 7.3 Assess Your Understanding - Page 559: 41

$a \approx10.44$ $B \approx24.5^\circ$ $C\approx 95.5^\circ$

1. Use the Law of Cosines, we have $a=\sqrt {(5)^2+(12)^2-2(5)(12)cos60^\circ}\approx10.44$ 2. Use the Law of Cosines, we have $B=cos^{-1}(\frac{(10.44)^2+(12)^2-(5)^2}{2(10.44)(12)})\approx24.5^\circ$ 3. We have $C\approx(180-60-24.5)=95.5^\circ$