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: 103

Answer

Verify the following identity: $(sin(y)^3 - csc(y)^3)/(sin(y) - csc(y)) = sin(y)^2 + csc(y)^2 + 1$

Work Step by Step

Verify the following identity: $(sin(y)^3 - csc(y)^3)/(sin(y) - csc(y)) = sin(y)^2 + csc(y)^2 + 1$ Cancel $csc(y) - sin(y)$ from the numerator and denominator. $(sin(y)^3 - csc(y)^3)/(sin(y) - csc(y))$ $= ((csc(y) - sin(y)) (csc(y)^2 + csc(y) sin(y) + sin(y)^2))/(csc(y) - sin(y))$ $= csc(y)^2 + csc(y) sin(y) + sin(y)^2$: $csc(y)^2 + csc(y) sin(y) + sin(y)^2 = ^?1 + csc(y)^2 + sin(y)^2$ Subtract $csc(y)^2 + sin(y)^2$ from both sides: $csc(y) sin(y) = ^?1$ Write cosecant as 1/sine: $1/(sin(y)) sin(y) = ^?1$ $(1/(sin(y))) sin(y) = 1$: $1 = ^?1$ The left hand side and right hand side are identical, thus verifying the identity.
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