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to use up vs to use Options
mcurrent
Posted: Friday, September 28, 2018 9:01:13 AM

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Joined: 7/6/2013
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Hi. Can you explain to me why author was writing "using up" rather than simple "use". The text in mathematical book is:

The story I heard while an undergarduate electrical engineering student goes like this: Imagine a three-dimensional plot, with the real (x) and imaginary (y) axes using up two dimensions to form the complex plane, and |f(z)| plotted on the third axis.

I am not able to feel difference of "to use" and "to use up".
thar
Posted: Friday, September 28, 2018 10:08:01 AM

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To use up is to exhaust your supply, to have none left.
So the only reason I can think of using it here is that you have a limited number of dimensions - 3, and the real and imaginary parts of the number take up two of them, leaving one left for the f(z).

I can't see any particular reason, other than that.

Maybe it is explaining why you can only plot the complex number against z, not against z and t, or whatever. I don't know. It is obviously trying to explain some concept, but presumably one more advanced than just how to plot complex numbers.

RuthP
Posted: Friday, September 28, 2018 3:28:25 PM

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Joined: 6/2/2009
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Location: Drain, Oregon, United States
thar wrote:
To use up is to exhaust your supply, to have none left.
So the only reason I can think of using it here is that you have a limited number of dimensions - 3, and the real and imaginary parts of the number take up two of them, leaving one left for the f(z).

I can't see any particular reason, other than that.

Maybe it is explaining why you can only plot the complex number against z, not against z and t, or whatever. I don't know. It is obviously trying to explain some concept, but presumably one more advanced than just how to plot complex numbers.

I think you are right, thar, but it would be helpful to know what |f(z)| represents. (Not that my mathematics is apt to be advanced enough to understand.)
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