# Write the complex number in rectangular form.

• May 6th 2013, 09:21 PM
boltage619
Write the complex number in rectangular form.
Write the complex number in rectangular form. 3cis52degrees ( round to 3 decimal places)
• May 6th 2013, 09:35 PM
MarkFL
Re: Write the complex number in rectangular form.
What does $\text{cis}(\theta)$ mean? What I mean, is use the definition, write it out, then use your calculator to evaluate the trig. functions.
• May 6th 2013, 09:40 PM
boltage619
Re: Write the complex number in rectangular form.
Cis = Cos * i sin
• May 6th 2013, 09:45 PM
MarkFL
Re: Write the complex number in rectangular form.
No, $\text{cis}(\theta)\equiv\cos(\theta)+i\sin(\theta)$.

So how would you expand $3\,\text{cis}\left(52^{\circ} \right)$ ?
• May 6th 2013, 09:50 PM
boltage619
Re: Write the complex number in rectangular form.
Wouldn't it be 3*cos52 + 3 * i sin52?
• May 6th 2013, 09:56 PM
MarkFL
Re: Write the complex number in rectangular form.
Yes, that's right, now just use your calculator to approximate the rectangular components. Rectangular form is:

$a+bi$ where $a,b\in\mathbb{R}$ (i.e. $a$ and $b$ are real.)

Here we have:

$a=3\cos\left(52^{\circ} \right)$

$b=3\sin\left(52^{\circ} \right)$
• May 6th 2013, 10:00 PM
boltage619
Re: Write the complex number in rectangular form.
I got 1.847+2.364i as my answer, is that right?
• May 6th 2013, 10:09 PM
MarkFL
Re: Write the complex number in rectangular form.
Yes, that's correct! Good work! :D
• May 6th 2013, 10:11 PM
boltage619
Re: Write the complex number in rectangular form.
Thank you! :D