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Calculator Tech Support =>
Technology & Calculator Open Topic
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WikiGuru
ADOS (Attention deficit... Oh! Shiny!)
Elite
Joined: 15 Sep 2005
Posts: 923
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 Posted: 26 Feb 2009 11:29:18 pm Post subject: |
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| I'm probably not the first person to realize this, but the TI-83+ SE doesn't convert complex numbers correctly ( I think the problem is only R e^(theta i) to a+bi , not the other way around). Has this been fixed at all for the 83+ SE? |
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simplethinker
snjwffl
Active Member
Joined: 25 Jul 2006
Posts: 700
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| Posted: 26 Feb 2009 11:32:30 pm Post subject: |
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| What do you mean by "doesn't convert complex numbers correctly"? |
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WikiGuru
ADOS (Attention deficit... Oh! Shiny!)
Elite
Joined: 15 Sep 2005
Posts: 923
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| Posted: 27 Feb 2009 12:22:20 am Post subject: |
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It doesn't convert polar complex numbers into rectangular complex number correctly.
Ex.:
R e^(theta * i)
R = 8.4
theta = -90 deg
correct answer:
a + bi
a = 8.4 cos(-90 deg) = 0
b = 8.4 sin(-90 deg) = 8.4
Calculator's answer:
-3.7638+-7.50957i
hmmm... I found the culprit. For some reason it's storing the complex polar numbers incorrectly, cause when I type in 8.4 e^(-90i) and press [ENTER], it returns 8.4 e^(-116.62i), which does convert to the calculator's answer |
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DarkerLine
ceci n'est pas une |
Super Elite (Last Title)
Joined: 04 Nov 2003
Posts: 8328
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| Posted: 27 Feb 2009 01:30:58 am Post subject: |
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| Yeah, e^( always uses radians, regardless of the degree/radian mode. This is because e^(180i)=-1 doesn't really make sense. But then, nothing about using degrees to measure angles makes sense. |
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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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| Posted: 27 Feb 2009 03:10:27 am Post subject: |
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In practical work with complex numbers, most tend to stick to radian measure, because the identities become much simpler, not having to carry very inconvenient factors of π/180 or its reciprocal.
At any rate, you should be entering the degree symbol anyway if you so very much insist on sticking to degrees.
thornahawk |
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WikiGuru
ADOS (Attention deficit... Oh! Shiny!)
Elite
Joined: 15 Sep 2005
Posts: 923
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| Posted: 27 Feb 2009 03:16:54 pm Post subject: |
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| Oh. That's kind of stupid, especially when working with phasors, which almost always are given in degrees. |
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simplethinker
snjwffl
Active Member
Joined: 25 Jul 2006
Posts: 700
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| Posted: 27 Feb 2009 03:30:22 pm Post subject: |
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| Radians are the natural unit of measurement, degrees are made-up by man. You can't do calculus (easily) in degrees or even calculate trigonometric functions without switching to radians. |
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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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| Posted: 27 Feb 2009 09:02:27 pm Post subject: |
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@simplethinker: As an aside, I used to have students take (nth) derivatives or integrals with trigonometric functions having degree units. That sure converted them pretty quick to using radian units... :)
@WikiGuru: as you know, "phasor" is merely a fancy term for polar-form complex numbers.  As I recall, the engineering schools are now trying to veer away from using degrees in practical work with phasors.
thornahawk |
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simplethinker
snjwffl
Active Member
Joined: 25 Jul 2006
Posts: 700
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| Posted: 27 Feb 2009 09:12:14 pm Post subject: |
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thornahawk wrote: @simplethinker: As an aside, I used to have students take (nth) derivatives or integrals with trigonometric functions having degree units. That sure converted them pretty quick to using radian units... 
All you have to do is add in an extra (pi/180)^n though! Making 7-digit trig tables is what finally converted me (long story short: 14 hour car ride) |
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WikiGuru
ADOS (Attention deficit... Oh! Shiny!)
Elite
Joined: 15 Sep 2005
Posts: 923
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| Posted: 28 Feb 2009 12:17:57 am Post subject: |
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| Strangely enough, in my ece class they put omega in radians, and then for the phase angle they put it in degrees. Is there a reason for this (other than tradition)? |
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thornahawk
μολών λαβέ
Active Member
Joined: 27 Mar 2005
Posts: 569
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| Posted: 28 Feb 2009 03:18:21 am Post subject: |
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"Is there a reason for this (other than tradition)?"
Well, since you specifically excluded tradition... ;)
thornahawk |
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