If you multiply two imaginary numbers

DSherry · 17 May 2009 at 22:44

xj * yj

is the answer always negative and a real number?

scorza · 17 May 2009 at 22:46

Not if I imagine the number 0.

caff · 17 May 2009 at 22:47

what is an imaginary number?

bemateer · 17 May 2009 at 22:47

depends on the coefficients x and y

eg: 1i *-1i = 1 as get i^2*-1 = -1*-1= 1

its always real if theres no other parts (ie to make it a complex number rather than just imaginary) but not always negative no

sorry ive used i instead of j being a mathmetician not engineer

ps caff an imaginary number is a number with coefficient (as it were) of the squareroot of minus 1. ie sqrt(-1)=i (or j)

TommyTenToes · 17 May 2009 at 22:48

Depends on the co-efficients x and y.

BigglesPiP · 17 May 2009 at 22:49

Oooh, electrical notation of the imaginary number.

TommyTenToes · 17 May 2009 at 23:12

BigglesPiP said:
Oooh, electrical notation of the imaginary number.

More of a general engineering notation as far as I'm aware?

nydryl · 17 May 2009 at 23:13

Why do they use j instead of i? I realise this is googleable but I'll ask anyway.

loltim · 17 May 2009 at 23:13

DSherry lol

rypt · 17 May 2009 at 23:14

nydryl said:
Why do they use j instead of i? I realise this is googleable but I'll ask anyway.

Because there is no i in team

p4radox · 17 May 2009 at 23:15

nydryl said:
Why do they use j instead of i? I realise this is googleable but I'll ask anyway.

i is used for small signal currents. Or something.

The answer if:

x&y are negative real: Negative Real
x&y are real, but one is negative: Positive Real
x&y are positive real: Negative Real
x or y is complex: It depends

TommyTenToes · 17 May 2009 at 23:16

nydryl said:
Why do they use j unstead of i?

I think it's due to i being used for certain currents.

Morba · 17 May 2009 at 23:19

Tim said:
DSherry lol

lolsherry D

Jotun · 17 May 2009 at 23:50

DSherry said:
xj * yj

is the answer always negative and a real number?

j*j=-1

so xj*yj = j*j*x*y = (-1)*x*y

Do the regular multiplication of x*y and multiply by -1

caff said:
what is an imaginary number?

As you can't have a square root of a negative number, i (or j for engineers) was introduced. It has a property that i*i=-1, and the square root of -1 = i.

They can be drawn in a 2D space with the x axis being the real dimension and the y axis being the imaginary axis.

As always, wikipedia has lots of information about it http://en.wikipedia.org/wiki/Imaginary_number

RoysonBobson · 17 May 2009 at 23:58

p4radox said:
i is used for small signal currents. Or something.

The answer if:

x&y are negative real: Negative Real
x&y are real, but one is negative: Positive Real
x&y are positive real: Negative Real
x or y is complex: It depends

Pretty good explanation.

Complex numbers = greatest invention/discovery ever.

PardonTheWait · 18 May 2009 at 00:11

FosterK · 18 May 2009 at 00:17

caff said:
what is an imaginary number?

Nixty-fleven.

rypt · 18 May 2009 at 00:19

RoysonBobson said:
Complex numbers = greatest invention/discovery ever.

Yes and no; they are useful; but they are also a pain as they mean you can do crazy 3d surfaces that intersect crazily and make your brain blow up

Gaygle · 18 May 2009 at 00:27

Surely it depends on the numbers you're thinking of?

Yrkoon · 18 May 2009 at 07:58

bemateer said:
depends on the coefficients x and y

eg: 1i *-1i = 1 as get i^2*-1 = -1*-1= 1

its always real if theres no other parts (ie to make it a complex number rather than just imaginary) but not always negative no

sorry ive used i instead of j being a mathmetician not engineer

ps caff an imaginary number is a number with coefficient (as it were) of the squareroot of minus 1. ie sqrt(-1)=i (or j)

please tell me im not the only one that is highly confused by this thread?

i failed at maths big time