Answer
$3cos\ u$
Work Step by Step
$\sqrt(9 - x^2)$, $x = 3 sin\ u$
We know that $ cos^2\ u+sin^2\ u=1$:
$\sqrt(9 - x^2)=\sqrt(9 - (3 sin\ u)^2)=\sqrt(9 - 9sin^2\ u)=3\sqrt(1 - sin^2\ u)=3\sqrt(cos^2\ u)=3cos\ u$
Precalculus: Mathematics for Calculus, 7th Edition
by Stewart, James; Redlin, Lothar; Watson, Saleem
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: 93
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