Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 7 - Applications of Trigonometric Functions - Section 7.1 Right Triangle Trigonometry ; Applications - 7.1 Assess Your Understanding - Page 540: 39

Answer

$c \approx 5.83$ $A \approx 59.0°$ $B \approx 31.0°$

Work Step by Step

Since we already have the measures of two of the sides of the triangle, we can use the Pythagorean theorem to figure out $c$, the length of the hypotenuse: $a^2 + b^2 = c^2$ Let's plug in the values we are given: $5^2 + 3^2 = c^2$ Evaluate the exponents: $25 + 9 = c^2$ Add on the left side of the equation: $34 = c^2$ Take the square root of both sides of the equation: $c = \sqrt {34}$ Evaluate the square root, rounding off to two decimal places: $c \approx 5.83$ To find the value of $A$, we can use one of the trig identities. Let's use the tangent identity: $\tan A = \frac{opposite}{adjacent}$ = $\frac{a}{b}$ We know that $a$ is $5$ and $b$ is $3$. Let's plug in these values into our formula so that we can find $A$: $\tan A = \frac{5}{3}$ Take the inverse tangent of both sides of the equation: $A = \tan^{-1} \left(\frac{5}{3}\right)$ Evaluate to solve for $A$, remembering to round off to one decimal place: $A \approx 59.0°$ To find $B$, we can use the tangent identity again: $\tan B = \frac{opposite}{adjacent}$ = $\frac{b}{a}$ We plug in the values we know into this formula: $\tan B = \frac{3}{5}$ Take the inverse tangent of both sides of the equation: $B = \tan^{-1} \left(\frac{5}{3}\right)$ Evaluate to solve for $B$, rounding the answer off to one decimal place: $B \approx 31.0°$
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