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: 43

Answer

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

Work Step by Step

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