Remove Imaginary Component from a Complex Number 1

[dik]

I've tried multiplying with the conjugate and ended up with a 'tiny' complex component. Does anyone know how to remove the imaginary component from a complex number. I'm using SMath.

Dik

Thanks

Dik

 

[3DDave]

https://smath.com/wiki/GetFile.aspx?File=Tutorials/IntrinsicNumericFunctions085.pdf

page 5 "Re(complex)" function.

 

[dik]

Thanks Dave... I found it in one of the articles.

Dik

 

[jhardy1]

Smath is doing something weird - I can replicate your result using Smath, but the same expressions entered into Mathcad Prime work fine.

Drilling down, it is apparent that the complex number is generated by the last term:

[tt]ln(-0.0339/(ln(1-1/n)))[/tt]

Checking the parameters shows that this should yield a real result, but for some reason it throws a complex result.

Bizarrely, if I do simple evaluation of this term, Smath gives a real solution; entering:

[tt]ln(-0.0339/(ln(0.8))) =[/tt]

yields the expected result: [tt]-1.8844[/tt]

However, saving this same expression into a variable, and then outputting the saved result, yields a complex result:

[tt]test := ln(-0.0339/(ln(0.8)))
test =[/tt]

yields a complex solution: [tt]-1.8844 + 3.1416 i[/tt]

Why this is so, I don't have a clue. However, "[tt]3.1416 i[/tt]" looks suspiciously like "[tt]pi i[/tt]", which is surely not a coincidence. I would guess it's some sort of glitch with storing the results of the log of a negative number divided by another negative number.

Hope this might help a little.

http://julianh72.blogspot.com

 

[IDS]

But why does it return a complex number?

When I do it in Excel I just get 17.73


Doug Jenkins
Interactive Design Services

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[IDS]

9 seconds too slow

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[IRstuff]

What version of SMath are you guys running? I'm using the most recent version and it doesn't seem to have this problem.

TTFN (ta ta for now)
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[dik]

IRS:
I'll check. I thought I was running the latest version.

Dik

 

[jhardy1]

I was using SMath Studio in the Cloud (web-based version), which you would assume is the latest code.

https://en.smath.com/cloud/

http://julianh72.blogspot.com

 

[IRstuff]

Well, that was weird. it turns out that my bad habit of using the immediate evaluation changed the outcome. I posted it as a bug in their bug tracker. Not sure how long it takes to get resolved; it looks like they've got a pretty long list

TTFN (ta ta for now)
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[3DDave]

Looks like this is not by itself.

https://en.smath.com/bts/Issues/IssueDetail.aspx?id=29

Interesting bug tracker - clicking the headings for sequential max at top, min at top, no sort; and works with multi-column sorts as well.

 

[IRstuff]

Looks like it's the same bug, which is BAD, given that it's been known for at least 2 years.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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