Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 6 - Section 6.1 - The Law of Sines - Exercise Set - Page 720: 15

Answer

$C=50{}^\circ,a\approx 7.1$ and $b\approx 7.1$.

Work Step by Step

First we will find the value of C. Properties of a triangle: The sum of three angles is $A+B+C=180{}^\circ $ $\begin{align} & A+B+C=180{}^\circ \\ & 65{}^\circ +65{}^\circ +C=180{}^\circ \\ & C=180{}^\circ -130{}^\circ \\ & C=50{}^\circ \end{align}$ Now, we will find the remaining sides using the ratio $\frac{c}{\sin C}$,or $\frac{6}{\sin 50{}^\circ }$, Now, we will use the law of sines to find a. $\begin{align} & \frac{a}{\sin A}=\frac{c}{\sin C} \\ & \frac{a}{\sin 65{}^\circ }=\frac{6}{\sin 50{}^\circ } \\ & a=\frac{6\sin 65{}^\circ }{\sin 50{}^\circ } \\ & a\approx 7.1 \end{align}$ Using the law of sines again, we will find b. $\begin{align} & \frac{b}{\sin B}=\frac{c}{\sin C} \\ & \frac{b}{\sin 65{}^\circ }=\frac{6}{\sin 50{}^\circ } \\ & b=\frac{6\sin 65{}^\circ }{\sin 50{}^\circ } \\ & b\approx 7.1 \end{align}$
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