Question

re-write in a+bi form

Answer 1

10(sq2)cis(7pi/4)

Answer 2

@perl

Answer 3

cis ???

Answer 4

cos i sin

Answer 5

u know cos i sin is equevelent of cot

Answer 6

haha this is a little different. the equation is
10(sq2)(cos(7pi/4)+isin(7pi/4)

Answer 7

\[\Large\rm 10\sqrt2\left[cis\left(\frac{7\pi}{4}\right)\right]\]What's up? 0_o we gotta turn this into a and b stuff?

Answer 8

yeep

Answer 9

So i guess multiply it in?

Answer 10

get your "special values" before you multiply it in

Answer 11

so its
\[10\sqrt{2}(\frac{ -\sqrt{2} }{ 2 }+i \frac{ \sqrt{2} }{ 2 })\]

Answer 12

hmm those looks backwards...
we're in quadrant 4, ya?
so cosine is positive,
sine negative.

Answer 13

what's going on with your profile picture? 0_o
too many legs and creepy things..
not enough light bulbs.

Answer 14

it's a Mexican walking fish!!

Answer 15

err not quite because it's coming from a whole other problem. I shall give you the link.

Answer 16

http://openstudy.com/users/babynini#/updates/555e9475e4b04f4769f35547

Answer 17

so you're on the division step, or what? :o

Answer 18

oh this must be the multiplication

Answer 19

I'm on the final step. So i got the answers but now it's asking me to put the results in form a+bi

Answer 20

Uhhh, ya your multiplication looks good :)
Hmm I still think you're getting the `signs` backwards though.

Answer 21

cosine positive, sine negative, ya?

Answer 22

oos, yeah I am. Sowriee

Answer 23

\[10\sqrt{2}[(\sqrt{2}/2)+i(-\sqrt{2}/2)]\]

Answer 24

cool :) then multiply in the stuff

Answer 25

em..that's my issue xD

Answer 26

Umm this might help to remember:\[\Large\rm \frac{\sqrt2}{2}=\frac{1}{\sqrt2}\]If you "un-rationalize it" it looks like that.
Maybe that will be easier to work with.

Answer 27

So this is our probelm:\[\Large\rm 10\sqrt2\left[\frac{1}{\sqrt2}-\frac{1}{\sqrt2}\mathcal i\right]\]wtf is up with these brackets? they're not formatting correctly :(

Answer 28

they're gorgeous, don't worry.

Answer 29

they're supposed to be nice and tall.. hmm maybe the website is bugging out..

Answer 30

soo the sq2 cancel out? i'ts just 10? :o

Answer 31

10-10i?

Answer 32

mmmmm ya looks good!

Answer 33

whaaat thats cray

Answer 34

that don't seem right bro haha

Answer 35

mmm k ill check :) sec

Answer 36

It probably is but it seems way simple x)

Answer 37

https://www.wolframalpha.com/input/?i=%28-5i%29%282%2B2i%29
notice that you can check your work very easily,\[\Large\rm (-5\mathcal i)(2+2\mathcal i)=-5\cdot2\mathcal i-5\cdot2\mathcal i^2\]\[\Large\rm =10-10\mathcal i\]

Answer 38

I mean, you can check your work very easily by NOT converting to cis.

Answer 39

oh. wow, that is a lot easier.
okies!!

Answer 40

I have one more question like this but i'll put it on another post :) thanks!