Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 10 - Geometry - 10.6 Right Triangle Trigonometry - Exercise Set 10.6 - Page 666: 32

Answer

The length of \[x\] is \[927\text{ units}\].

Work Step by Step

In triangle ABC, Let the side adjacent to \[48{}^\circ \] is \[a\]. Compute the value of \[a\] using the equation as shown below: \[\begin{align} & \text{Tan}\theta =\frac{\text{Side Opposite to angle}}{\text{Adjacent side to angle}}=\frac{AB}{BC} \\ & \text{Tan}48{}^\circ =\tfrac{500}{a}\text{ } \\ & 1.11=\tfrac{500}{a} \end{align}\] On cross multiplying, we get \[\begin{align} & a=\tfrac{500}{1.11} \\ & a=450.45 \\ \end{align}\] In triangle ABD, Let the side adjacent to\[{{20}^{\circ }}\] is \[x+a\]. Compute the value of \[x\] using the equation as shown below: \[\begin{align} & \text{Tan}\theta =\frac{\text{Side Opposite to angle}}{\text{Adjacent side to angle}}=\frac{AB}{BD} \\ & \text{Tan}{{20}^{\circ }}=\tfrac{500}{x+a} \\ & 0.363=\tfrac{500}{x+a} \end{align}\] On cross multiplying both sides, we get \[\begin{align} & 0.363(x+a)=500 \\ & 0.363(x+450.45)=500 \\ & 0.363x+\left( 0.363\times 450.45 \right)=500 \\ & 0.363x+163.5=500 \end{align}\] \[\begin{align} & 0.363x=500-163.5 \\ & 0.363x=336.49 \end{align}\] On dividing both sides by \[0.363\], we get \[\begin{align} & x=\tfrac{336.49}{0.363} \\ & x=926.96\text{ units} \end{align}\] Hence, the length of \[x\] to the nearest whole number is \[927\text{ units}\].
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