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Mathematics 8 Online
OpenStudy (babynini):

Find indicated power using DeMovire's theorem Write in a+bi form.

OpenStudy (babynini):

\[(3\sqrt{3}+3i)^{-5}\]

OpenStudy (babynini):

I already solved it but the numbers are pretty outrageous so I just want to check that I didn't do it wrong o.0

OpenStudy (babynini):

@rvc

OpenStudy (babynini):

@rvc it doesn't let me msg you since you've not fanned me. Thank you anyway:) do you know someone who does know?

zepdrix (zepdrix):

0_o

zepdrix (zepdrix):

Okie I check :O

OpenStudy (babynini):

Yay! thank you :)

zepdrix (zepdrix):

So before I turn it into a+bi, I'm getting something like this,\[\Large\rm 6^{-5}\left[\cos\left(-\frac{5\pi}{6}\right)+\mathcal i \sin\cos\left(-\frac{5\pi}{6}\right)\right]\]

zepdrix (zepdrix):

That what you're getting? :O These numbers are not outrageous, so I'm thinking you got something else? 0_o

OpenStudy (babynini):

oh gosh...so when I was finding r and got to where i'm mean to square 36 i wrote it like (36)^(1/2) and put the answer as 18 because I divided it instead of sq rooting it *facepalm. epic fail.

zepdrix (zepdrix):

XD

zepdrix (zepdrix):

How did you find your r? Using the weird square root and all that jazz?

zepdrix (zepdrix):

I have different method :O Maybe too crazy for you though.

OpenStudy (babynini):

Um I found it by doing \[r= ((3\sqrt{3})^{2}+(3)^{2})^{1/2}\]

OpenStudy (babynini):

haha hrm, well you can try teaching to me, but it might just confuse me more xD

OpenStudy (babynini):

I mean, this method is pretty straight forward I think

zepdrix (zepdrix):

Hmm yah maybe I don't wanna confuse you :d

OpenStudy (babynini):

\[z ^{-5}=-3888(-\sqrt{3})+(-3888i)\] is the final answer then?

OpenStudy (babynini):

lol ,thanks. I appreciate that ;P

zepdrix (zepdrix):

Hmm I don't understand your answer....

zepdrix (zepdrix):

It was a -5 exponent, so our radial length is really really really short. 6^(-5)

zepdrix (zepdrix):

So each component should be multiplied by, \(\Large\rm \frac{1}{6^5}=\frac{1}{7776}\)

OpenStudy (babynini):

right, so then I got -7776(-sq3/2) + i(-1/2) so when i factor it in it gets divided by two. yeah?

zepdrix (zepdrix):

\[\Large\rm =6^{-5}\left[\cos\left(-\frac{5\pi}{6}\right)+\mathcal i \sin\cos\left(-\frac{5\pi}{6}\right)\right]\]\[\Large\rm =6^{-5}\left[-\frac{\sqrt3}{2}-\frac{1}{2}\mathcal i\right]\]Again, I'm confused about your radius. You have -7776. Your radius should be a positive length.

zepdrix (zepdrix):

You should have 1/7776 for your radius.

zepdrix (zepdrix):

Looks good besides that though.

OpenStudy (babynini):

Isn't when something raised to a negative power it's still negative? o.0

OpenStudy (babynini):

ooh or when it's multiplied in it will become positive?

zepdrix (zepdrix):

Dat Miriam :O She so silly. Go plant another light bulb! Did you get this for your radius \(\Large\rm 6^{-5}\), yes no?

OpenStudy (babynini):

lol xD Yes I did.

zepdrix (zepdrix):

So then,\[\Large\rm 6^{-5}=\frac{1}{6^5}=\frac{1}{7776}\]Just forgetting your exponent rules maybe?

OpenStudy (babynini):

but.. I don't want it under a 1.

zepdrix (zepdrix):

|dw:1432014848138:dw|No? Why not?

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