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11-22-2018
06:23 AM

11-22-2018
06:23 AM

I can not use mathematic expression with "j" ( complex number)

Hi all

I am doing a calculation of RLC circuit in MathCAD, but I am facing to a problem with usage of "i" ( notation of complex number) as shown bellow:

Please help me to treat this .

Best regards,

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10 REPLIES 10

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11-28-2018
01:17 AM

11-28-2018
01:17 AM

Re: I can not use mathematic expression with "j" ( complex number)

Hi. In Mathcad imaginary unit is 1i or 1j, but shows just i or j.

Best regards.

Alvaro.

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11-28-2018
02:40 PM

11-28-2018
02:40 PM

Re: I can not use mathematic expression with "j" ( complex number)

Mathcad Prime - new in complex number formatting

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11-28-2018
02:45 PM

11-28-2018
02:45 PM

Re: I can not use mathematic expression with "j" ( complex number)

I have seen a lot of Mathcad-sheets with:

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11-28-2018
03:06 PM

11-28-2018
03:06 PM

Re: I can not use mathematic expression with "j" ( complex number)

See please - with units

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12-27-2018
02:46 PM

12-27-2018
02:46 PM

Re: I can not use mathematic expression with "j" ( complex number)

Works for me if I define j as the square root of -1

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12-27-2018
02:53 PM

12-27-2018
02:53 PM

Re: I can not use mathematic expression with "j" ( complex number)

@W3EO wrote:

Works for me if I define j as the square root of -1

In real Mathcad (=MC15 and below) I would strongly advise against doing so, but in Prime I have to admit that the imaginary unit displayed as 1j or 1i simply looks too ugly and so I understand that defining j:=1i or something like that makes sense.

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12-30-2018
01:45 AM

12-30-2018
01:45 AM

Re: I can not use mathematic expression with "j" ( complex number)

Yes, in "Real" Mathcad 🙂 I'll never assimilate the Primes. I have always defined the imaginary constant explicitly, as it gives me the confidence that I'm using the values I want. Why do you think this is bad practice?

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12-30-2018
05:06 AM

12-30-2018
05:06 AM

Re: I can not use mathematic expression with "j" ( complex number)

You may run into troubles with symbolics not understanding your definition of the imaginary unit...?

Luc

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12-30-2018
06:39 AM

12-30-2018
06:39 AM

Re: I can not use mathematic expression with "j" ( complex number)

@aroberts wrote:

First of all: Why define a constant which is already predefined in the software?

And then: From a mathematical point of view its simply wrong to say that i=sqrt(-1). You may run into severe troubles if you do so. But its OK to say that i^2=-1. i is one of the two solutions of the equation z^2+1=0 and it does not matter at all which of the two.

You may want to have a look at https://en.wikipedia.org/wiki/Imaginary_unit#Definition and the next two chapters there.

BTW, Wolfram as so often disagrees with mathematical conventions and definitions and thinks its OK to define i=sqrt(-1) -> http://mathworld.wolfram.com/ImaginaryUnit.html

So its up to you if you want trust Wolfram or trust Math 😉

The definition of i was seen quite controversy as long as I can remember and you sure may look at it as some purely academic squabble. You may be interested in discussions on stackexchange

https://math.stackexchange.com/questions/887724/refining-my-knowledge-of-the-imaginary-number

https://math.stackexchange.com/questions/1387820/a-proper-definition-of-i-the-imaginary-unit

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12-30-2018
01:41 PM

12-30-2018
01:41 PM

Re: I can not use mathematic expression with "j" ( complex number)

That is interesting and I appreciate the explanation