Answer
$1$
Work Step by Step
$\sin \dfrac {\pi }{5}\cos \dfrac {3\pi }{10}+\cos \dfrac {\pi }{5}\sin \dfrac {3\pi }{10}=\sin \left( \dfrac {\pi }{5}+\dfrac {3\pi }{10}\right) =\sin \dfrac {\pi }{2}=1$
Precalculus (6th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
013421742X
ISBN 13:
978-0-13421-742-0
Chapter 7 - Trigonometric Identities and Equations - 7.3 Sum and Difference Identities - 7.3 Exercises - Page 679: 59
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