Please help with spec homework

[ejf8888]

Hi,

There are a couple of questions on my homework sheet that im not sure of, mainly about Cis and rectangular form and which one to leave the answer in. Any help would be greatly appreciated!!

1. Simplify (2Cis(-2pie/3))^5.

I got the answer 32Cis(-3pie/4). Im not sure whether Im supposed to leave it in Cis form or change it to rectangular.

2. Find the conjugate of 2Cis(-2pie/3).

I wasnt sure how to find the conjugate while it was still in Cis form so i changed it to rectangular and got -1 + ((3)^1/2)i. Am i allowed to leave it like that or should i change it back to Cis form?

Thankyou in advance for any help!

[kamil9876]

1.) it depends what is specified in th question. Since nothing is specified u r justified to leave it as it is

2.) a quicker way of finding the conjugate is to negate the angle. i.e: and are conjugates of each other. To justify this, sketch the numbers and on the argand plane and notice the symmetry about the x-axis

[TrueTears]

As kamil said for Q 2, the conjugate of is . Question does not state to leave in any type of form, so you can leave it in polar form.

[ejf8888]

Cool! I didnt realise that about the conjugate.

Thanks guys!