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Mathematics 7 Online
OpenStudy (anonymous):

Complex numbers!

OpenStudy (anonymous):

OpenStudy (anonymous):

took me forever and I still have no clue.

OpenStudy (anonymous):

or should i just guess

OpenStudy (anonymous):

lol

zepdrix (zepdrix):

\[\Large \left(-1+i \sqrt3\right)^{1/3}\]Factoring out a 2 from each term,\[\Large 2^{1/3}\left(-\frac{1}{2}+i\frac{\sqrt3}{2}\right)^{1/3}\]These values come frommmmm an angle of 2pi/3 or 120 degrees,\[\Large 2^{1/3}\left(\cos120+i \sin120\right)^{1/3}\]Using Euler's Formula we can write it like this,\[\Large 2^{1/3}\left(e^{120i}\right)^{1/3} \qquad=\qquad 2^{1/3}e^{40i}\] Going back to the form we had before,\[\Large 2^{1/3}e^{40i}=2^{1/3}\left(\cos40^o+i \sin40^o\right)\] Hmm I wouldn't really know how to explain this to you :( I don't know much about complex numbers. There's probably a much easier way than the approach I took.

zepdrix (zepdrix):

Did you take your Trig Exam today? :)

OpenStudy (anonymous):

it was horrible omg

OpenStudy (anonymous):

i had to take both a midterm and final

zepdrix (zepdrix):

oh boy :(

OpenStudy (anonymous):

at the same time

OpenStudy (anonymous):

i answered almost everything except for vectors

zepdrix (zepdrix):

oh good :O

OpenStudy (anonymous):

not really :/

OpenStudy (anonymous):

i tried filling up everything and not leaving unanswered stuff

OpenStudy (anonymous):

OH btw is the answer D x3

zepdrix (zepdrix):

D? Yah that's what I came up with D:

zepdrix (zepdrix):

But I dunno if I can explain it in a clear way. There is some formula Louv.... something? That allows you to do these a bit easier... I forget what it's called...

zepdrix (zepdrix):

Oh oh `DeMoivre's Theorem`, does that sound familiar?

OpenStudy (anonymous):

yeah

OpenStudy (anonymous):

idk that theorem

OpenStudy (anonymous):

i have to use it to change this complex number : (1-isqrt(3))^3 into trig form

zepdrix (zepdrix):

omg site crashed again :( I lost of the stuff i was writing... so frustrating... I dunno what's going on lately, this thing is so unstable :C

OpenStudy (anonymous):

:o oh no try writing it somewhere else and copy and paste?

zepdrix (zepdrix):

ya maybe I'll try that :c

OpenStudy (anonymous):

nah its cool i figured it out xD

zepdrix (zepdrix):

ok cool c: sorry

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