Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 7 - Section 7.1 - Trigonometric Identities - 7.1 Exercises - Page 544: 79

Answer

True.

Work Step by Step

Verify the following identity: $\frac{sin(w)}{sin(w) + cos(w)}=\frac{tan(w)}{1 + tan(w)}$ Multiply numerator and denominator of $\frac{sin(w)}{sin(w) + cos(w)}$ by $sec(w)$: $\frac{sec(w)sin(w)}{sec(w)(sin(w) + cos(w))} = ^?(tan(w))/(1 + tan(w))$ Since $sec(w)sin(w) = tan(w)$: $\frac{tan(w)}{sec(w)(cos(w) + sin(w))} = ^?(tan(w))/(1 + tan(w))$ Since $sec(w) (cos(w) + sin(w)) = cos(w) sec(w) + sec(w) sin(w) $ $= \frac{cos(w)}{cos(w)}+ \frac{sin(w)}{cos(w)} = 1 + \frac{sin(w)}{cos(w)} = 1 + tan(w)$: $\frac{tan(w)}{1 + tan(w)} = ^?\frac{tan(w)}{1 + tan(w)}$ The left hand side and right hand side are identical, thus verifying the identity.
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