Trigonometry (10th Edition)

Published by Pearson
ISBN 10: 0321671775
ISBN 13: 978-0-32167-177-6

Chapter 7 - Applications of Trigonometry and Vectors - Section 7.1 Oblique Triangles and the Law of Sines - 7.1 Exercises - Page 299: 50

Answer

$84.40$ m$^{2}$

Work Step by Step

First, we need to find the length of the side $c$ in order to use the formula for the Area of the triangle (SAS): For this, we first find the angle $B$: $A^{\circ}+B+C^{\circ}=180^{\circ}$ $59.8^{\circ}+B+53.1^{\circ}=180^{\circ}$ $112.9^{\circ}+B=180^{\circ}$ $B=180^{\circ}-112.9^{\circ}$ $B=67.1^{\circ}$ Now, we use the sine rule to find the length of the side $c$: $\frac{b}{\sin B}=\frac{c}{\sin C}$ $\frac{15}{\sin 67.1}=\frac{c}{\sin 53.1}$ $c=\frac{15\times\sin 53.1}{\sin 67.1}$ $c=\frac{15\times 0.79968}{0.92119}$ $c=13.021$ The area of the triangle is half the product of the length of two sides and the sine of the angle included between them: $Area=\frac{1}{2}bc \sin A$ We substitute the values of $A,b$ and $c$ in this formula and solve: $Area=\frac{1}{2}bc \sin A$ $Area=\frac{1}{2}(15)(13.021) \sin 59.8^{\circ}$ $Area=\frac{1}{2}(195.315) \sin 59.8^{\circ}$ $Area=97.658\sin 59.8^{\circ}$ Using a calculator, $\sin 59.8^{\circ}=0.86427$. Therefore, $Area=97.658\sin 59.8^{\circ}$ $Area=97.658(0.86427)$ $Area=84.40$ Therefore, the area of the triangle is $84.40$ m$^{2}$.
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