#### Answer

$3i$

#### Work Step by Step

We know that $\cos90^{\circ}=0$ and $\sin90^{\circ}=1$
Substituting these values in the expression and solving:
$3(\cos90^{\circ}+i\sin90^{\circ})=3(0+1i)=3i$
Therefore, the rectangular form is $3i$.

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Published by
Pearson

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

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

$3i$

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