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: 5

Answer

Value of \[\sin A=\frac{5}{13}\], \[\cos A=\frac{12}{13}\], and \[\tan A=\frac{5}{12}\].

Work Step by Step

Length of hypotenuse that is \[\left( c=26 \right)\], Side opposite to acute angle A that is \[\left( a=10 \right)\]. Firstly, it is required to compute side adjacent to acute angle A that is b using the Pythagorean Theorem as follows: The side adjacent to acute angle A, that is b of a triangle, is given by the formula: \[\begin{align} & c\text{ }=\sqrt{{{a}^{2}}+{{b}^{2}}} \\ & \text{26 }=\sqrt{{{10}^{2}}+{{b}^{2}}} \\ & {{26}^{2}}={{10}^{2}}+{{b}^{2}} \\ & 676=100+{{b}^{2}} \end{align}\] Further it can be simplified as: \[\begin{align} & {{b}^{2}}=676-100 \\ & {{b}^{2}}=576 \end{align}\] Take square root both the sides as follows: \[\begin{align} & {{b}^{2}}=\sqrt{576} \\ & \text{b }=24 \end{align}\] Now, compute the different trigonometric ratios using the formulas: \[\begin{align} & \sin A=\frac{\text{Side opposite to angle }A}{\text{Hypotenuse}} \\ & =\frac{10}{26} \\ & =\frac{5}{13} \end{align}\] Therefore, \[\sin A=\frac{5}{13}\] \[\begin{align} & \cos A=\frac{\text{Side adjacent to angle }A}{\text{Hypotenuse}} \\ & =\frac{24}{26} \\ & =\frac{12}{13} \end{align}\] Therefore, \[\cos A=\frac{12}{13}\] \[\begin{align} & \text{tan }A=\frac{\text{Side opposite angle }A}{\text{Side adjacent to angle }A} \\ & =\frac{10}{24} \\ & =\frac{5}{12} \end{align}\] Therefore, \[\tan A=\frac{5}{12}\] Hence, the value of trigonometric ratios is, \[\sin A=\frac{5}{13}\], \[\cos A=\frac{12}{13}\], and \[\tan A=\frac{5}{12}\].
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