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 665: 6

Answer

Value of \[\sin A=\frac{9}{41}\], \[\cos A=\frac{40}{41}\], and \[\tan A=\frac{9}{40}\].

Work Step by Step

The length of hypotenuse that is \[\left( c=41 \right)\], Side adjacent to acute angle A that is \[\left( b=40 \right)\]. Firstly, compute side opposite to acute angle A\[\left( a \right)\], using the Pythagorean Theorem. The side opposite to acute angle A\[\left( a \right)\]of a triangle is given by the formula: \[\begin{align} & c\text{ }=\sqrt{{{a}^{2}}+{{b}^{2}}} \\ & \text{41 }=\sqrt{{{a}^{2}}+{{40}^{2}}} \\ & {{41}^{2}}={{a}^{2}}+{{40}^{2}} \\ & 1681={{a}^{2}}+1600 \end{align}\] Further it can be simplified as: \[\begin{align} & {{a}^{2}}=1681-1600 \\ & {{a}^{2}}=81 \end{align}\] Take square root both the sides as follows: \[\begin{align} & \sqrt{{{a}^{2}}}=\sqrt{81} \\ & a\text{ }=9 \end{align}\] Now, compute the different trigonometric ratios using the formulas: \[\begin{align} & \sin \text{ }A=\frac{\text{Side opposite to angle }A}{\text{Hypotenuse}} \\ & =\frac{9}{41} \end{align}\] Therefore, \[\sin A=\frac{9}{41}\] \[\begin{align} & \cos \text{ }A=\frac{\text{Side adjacent to angle }A}{\text{Hypotenuse}} \\ & =\frac{40}{41} \end{align}\] Therefore, \[\cos A=\frac{40}{41}\] \[\begin{align} & \text{tan }A=\frac{\text{Side opposite angle }A}{\text{Side adjacent to angle }A} \\ & =\frac{9}{40} \end{align}\] Therefore, \[\tan A=\frac{9}{40}\] Hence, the value of trigonometric ratios is, \[\sin A=\frac{9}{41}\], \[\cos A=\frac{40}{41}\], and \[\tan A=\frac{9}{40}\].
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