re^itheta

**jzellt** · October 11th 2010, 08:29 PM

I'm asked to express 4 in the form re^i*theta

Here's what i've done:

r = squreRoot(4^2 + 0^2)
r = 4

How do I find theta?

**Defunkt** · October 11th 2010, 08:31 PM

$4 = 4 +0\cdot i$ , so $\theta = arctan \left( \frac{0}{4} \right) = arctan(0)$

**jzellt** · October 11th 2010, 08:51 PM

Ok, then 4 written in this form is just simply 4 since 4e^i*0 = 4. RIght?

How about this one: 3i

r = 3, but theta = arctan(3/0)??? 3 divided by 0...

**Prove It** · October 12th 2010, 12:40 AM

Well, $3i$ lies on the positive imaginary axis.

What is the angle made?

**mr fantastic** · October 12th 2010, 01:30 AM

Originally Posted by jzellt

I'm asked to express 4 in the form re^i*theta

Here's what i've done:

r = squreRoot(4^2 + 0^2)
r = 4

How do I find theta?

Originally Posted by jzellt

[snip]
How about this one: 3i

r = 3, but theta = arctan(3/0)??? 3 divided by 0...

If you had plotted 4 and 3i on an Argand diagram it would be completely obvious what the argument of each is.

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