# Math Help - express in rectangular form

1. ## express in rectangular form

Hi all, will you please assist

z=2cis120º

Nice day all

2. Hello, nunuza!

Do you know the meaning of "cis"?

Express in rectangular form: . $z \:=\:2\!\cdot\!\text{cis}(120^o)$
$2\!\cdot\!\text{cis}(120^o) \;=\;2\left(\cos120^o + i\sin120^o\right) \;=\;2\left(-\frac{1}{2} + i\frac{\sqrt{3}}{2}\right) \;= \;-1+ i\sqrt{3}$

3. ## cis's meaning

Hi SOroban

I only know it has to do with complex numbers, if u know please share.
THANX!!

4. Originally Posted by neoza
Hi SOroban

I only know it has to do with complex numbers, if u know please share.
THANX!!
cis( $\theta$) = cos( $\theta$) + i sin( $\theta$)