Answer
$2.69,3.59$
Work Step by Step
Use a calculator, $cos\theta=-0.9 \Longrightarrow \theta=cos^{-1}(-0.9)\approx2.69$ and $2\pi-2.69\approx3.59$ in $[0,2\pi)$.
Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)
by Sullivan III, Michael
Published by
Pearson
ISBN 10:
0-32193-104-1
ISBN 13:
978-0-32193-104-7
Chapter 6 - Analytic Trigonometry - Section 6.3 Trigonometric Equations - 6.3 Assess Your Understanding - Page 488: 49
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