How do you write $3(cos(90)+isin(90))$ in rectangular form?

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Answer 1 · 2015-02-04T19:10:08

I think you are working in degrees here, so you simply multiply $3$ times whatever you have inside your brackets.

In this case:

$cos(90°)=0$
$sin(90°)=1$

So you get:

$z=3(cos(90°)+isin(90°))=3*(0+i*1)=3i$

Your number is a pure imaginary.

You can also see this by plotting your complex number $z$ on the complex plane:
enter image source here

hope it helps

How do you write 3(cos(90)+isin(90))3(cos(90)+isin(90)) in rectangular form?