Trigonometry 7th Edition

Published by Cengage Learning
ISBN 10: 1111826854
ISBN 13: 978-1-11182-685-7

Chapter 5 - Section 5.2 - Sum and Difference Formulas - 5.2 Problem Set - Page 289: 44

Answer

$\sin{(A-B)} = \dfrac{63}{65}$ $ \cos{(A-B)} = \dfrac{16}{65}$ $\tan{(A-B)} = \dfrac{63}{16}$ $QI$

Work Step by Step

$\sin{A} = \sqrt{1-(\dfrac{-5}{13})^2} = \dfrac{12}{13}$ $\cos{B} = \sqrt{1-(\dfrac{4}{5})^2} = \dfrac{4}{5}$ $\sin{(A-B)} = \sin{A} \cos{B} - \cos{A} \sin{B}$ $\sin{(A-B)} = \dfrac{12}{13} \times \dfrac{4}{5}- \dfrac{3}{5} \times \dfrac{-5}{13}$ $\sin{(A-B)} = \dfrac{63}{65}$ $\cos{(A-B)} = \cos{A} \cos{B} + \sin{A} \sin{B}$ $\cos{(A-B)} = \dfrac{-5}{13} \times \dfrac{4}{5} + \dfrac{12}{13} \times \dfrac{3}{5} $ $ \cos{(A-B)} = \dfrac{16}{65}$ $\tan{(A-B)} = \dfrac{\sin{(A-B)}}{\cos{(A-B)}} = \dfrac{63}{16}$ $\sin{(A-B)} > 0 \hspace{20pt} \cos{(A-B)} > 0 \hspace{20pt} \therefore QI$
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