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 667: 34

Answer

The length of\[x\]is\[481\text{ units}\].

Work Step by Step

In triangle ABC, Let the side adjacent to \[\text{angle }43{}^\circ \] is\[a\]. Compute the length of \[x\]using the trigonometric function of Tangent as follows: \[\begin{align} & \text{Tan}\theta =\frac{\text{Side Opposite to angle}}{\text{Adjacent side to angle}}=\frac{AB}{BC} \\ & \text{Tan}{{43}^{\circ }}=\tfrac{x}{a} \\ & \text{Tan}{{43}^{\circ }}=0.9325 \\ & \tfrac{x}{a}=0.9325 \end{align}\] On multiplying both sides by\[a\], we get. \[x=0.9325a\] In triangle ABD, Let the side adjacent to \[{{38}^{\circ }}\]is\[a+100\]. Compute the length of the x using the trigonometric function of Tangent as follows: \[\begin{align} & \text{Tan}\theta =\frac{\text{Side Opposite to angle}}{\text{Adjacent side to angle}}=\frac{AB}{BD} \\ & \text{Tan}{{38}^{\circ }}=\tfrac{x}{100+a} \\ & 0.7812=\tfrac{0.9325a}{100+a} \end{align}\] On cross multiplying both sides, we get \[\begin{align} & 0.9325a=0.7812(100+a) \\ & 0.9325a=0.7812\times 100+0.7812a \\ & 0.9325a=78.12+0.7812a \\ & 0.1513a=78.12 \end{align}\] On dividing both sides by\[0.1513\], we get \[\begin{align} & a=\frac{78.12}{0.1513} \\ & =516.325 \end{align}\] Now, on putting the value of a in the value of x, we get \[\begin{align} & x=0.9325a \\ & =0.9325\times 516.325 \\ & =481\text{ units} \end{align}\] The length of x to the nearest whole number is\[481\text{ units}\].
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