# Complex Numbers Calculation Help!!!

#### babaliaris

Can you tell me what I did wrong? I really can't find the mistake!

Here is my problem

Also if you can't see it Ohms * Amperts = Volts

The result should be: 144,3kv * angle(4,93)

Last edited by a moderator:

#### jks

Hi babaliaris,

I think that your calculation for $\large \tan^{-1} \left (\frac{20}{6} \right )$ is incorrect. Using the value that I calculated, I arrived at the given answer.

#### babaliaris

Hi babaliaris,

I think that your calculation for $\large \tan^{-1} \left (\frac{20}{6} \right )$ is incorrect. Using the value that I calculated, I arrived at the given answer.
Thank you very much!!! The problem was with my new scientific calculator; I wasn't using it correctly.

At least now I know that my logic is correct.

One more question. Can I do this calculation faster?
Our Professor said to us "When you want to add two Complex Numbers, you use the Cartesian form and when you want to multiply you use the polar form."

So every time when I do a calculation I need to convert the numbers from Cartesian form to polar and the opposite depending on what I'm doing.

Last edited by a moderator:

#### jks

One more question. Can I do this calculation faster?
Our Professor said to us "When you want to add two Complex Numbers, you use the cartesian form and when you want to multiply you use the polar form."
Maybe someone has a better way, but I just do it as your Professor says.

Last edited by a moderator:

#### babaliaris

Maybe someone has a better way, but I just do it as your Professor says.
Yeah, probably this is the only way, but anyway thank you for your help!!!

Last edited by a moderator:

#### mathman

Forum Staff
Thank you very much!!! The problem was with my new scientific calculator; I wasn't using it correctly.

At least now I know that my logic is correct.

One more question. Can I do this calculation faster?
Our Professor said to us "When you want to add two Complex Numbers, you use the Cartesian form and when you want to multiply you use the polar form."

So every time when I do a calculation I need to convert the numbers from Cartesian form to polar and the opposite depending on what I'm doing.
You can use the Cartesian form for all arithmetic operations. Unless you are multiplying many numbers together, it is just as fast as polar. On the other hand, polar is very hard (if not impossible) for addition.

Last edited by a moderator: