Chapter 7 - Applications of Trigonometric Functions - Section 7.3 The Law of Cosines - 7.3 Assess Your Understanding - Page 559: 42

$A \approx41.4^\circ$ $B \approx41.4^\circ$ $C\approx 97.2^\circ$

1. Use the Law of Cosines, we have $A=cos^{-1}(\frac{(10)^2+(15)^2-(10)^2}{2(10)(15)})\approx41.4^\circ$ 2. It is an isosceles triangle $B=A\approx41.4^\circ$ 3. We have $C\approx(180-41.4-41.4)=97.2^\circ$