#### Answer

$3(cos 90^\circ + isin90^\circ)$.

#### Work Step by Step

$3i$ is at $90^\circ$ with absolute value $\sqrt{0^2 + 3^2} =3$, the equivalent trigonometric form is $3cis90^\circ$ or $3(cos 90^\circ + isin90^\circ)$.

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Published by
Pearson

ISBN 10:
978-0-13-421743-7

ISBN 13:
978-0-13421-743-7

$3(cos 90^\circ + isin90^\circ)$.

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