#### Answer

$\pm 1$

#### Work Step by Step

$r^{2}=-2\cos 2\theta \Rightarrow r^{2}=-2\cos \left( 2\times 60\right) =-2\cos 120=-2\times \left( -\dfrac {1}{2}\right) =1\Rightarrow r=\pm 1$

Published by
Pearson

ISBN 10:
013421742X

ISBN 13:
978-0-13421-742-0

$\pm 1$

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