## Thinking Mathematically (6th Edition)

Published by Pearson

# Chapter 10 - Geometry - Chapter Summary, Review, and Test - Review Exercises: 61

#### Answer

$c \approx 23 \text{ cm}$

#### Work Step by Step

RECALL: In a right triangle, $\sin{A} = \dfrac{\text{length of opposite side}}{\text{length of hypotenuse}}$ $\cos{A} = \dfrac{\text{length of adjacent side}}{\text{length of hypotenuse}}$ $\tan{A} = \dfrac{\text{length of opposite side}}{\text{length of adjacent side}}$ Use the sine formula above to obtain: $\sin{61^o} = \dfrac{20}{c}$ Cross-multiply to obtain: $c \cdot \sin{61^o} = 20$ Divide $\sin{61^o}$ on both sides of the equation to obtain: $c = \dfrac{20}{\sin{61^o}}$ Use a scientific calculator to obtain: $c = 22.86708136 \\c \approx 23 \text{ cm}$

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