Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 7 - Analytic Trigonometry - 7.5 Sum and Difference Formulas - 7.5 Assess Your Understanding - Page 487: 29



Work Step by Step

Recall that: $\tan(\alpha+\beta)=\dfrac{\tan(\alpha)+\tan(\beta)}{1-\tan(\alpha)\tan(\beta)}$. Hence, $\dfrac{\tan(20^\circ)+\tan(25^\circ)}{1-\tan(20^\circ)\tan(25^\circ)}=\tan(20^\circ+25^\circ)=\tan(45^\circ)=1$
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