Re: TI-92 Phasor question

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Re: TI-92 Phasor question

Congratulations, you have discovered a bug that occurs when you are
using complex notation in degree format (which I by the way would
avoid since it is so uncommon). Here is an explanation of the bug.


Apparently the 92 interpret the input as radians (despite the degree
mode setting), simplifies it, and then converts the simplified value
to degrees at output.


When you input


e^(-70.0*i)


and try to store it in variable b, the calculator interprets it as
radians and simplifies it to


e^(-70.0*i)=e^((-70.0+22*Pi)*i)=e^(-0.8849616*i)


Then it converts


-0.8849616 radians=-0.8849616*180/Pi degrees=-50.7045659157 degrees


The expression e^(-50.70456*i) is stored in the variable b


When you type b it interprets the argument again as radians and
simplifies it


e^(-50.70456*i)=e^((-50.70456+16*Pi)*i)=e^(-0.43908345*i)


Then it converts


-0.43908345 radians=-0.43908345*180/Pi degrees=-25.157629 degrees


and gives e^(-25.157629*i) as output.


It is easier to follow the bug if you instead use a fraction of Pi
as an input.


This is a rather serious bug that must be corrected in future ROM
versions (I have version 1.11) so it is good that you have reported
the problem to TI.


Richard Schatz
Laboratory of Photonics and Microwave Eng.
Royal Institute of Technology
Stockholm


  Randall Vogtman wrote:
> While performing phasor (Steinmetz) calculations with my new TI-92, I've
> come across a problem where I don't believe a variable is storing
> correctly.
> I've sent a question off to ti-cares, but I thought I'd try here also.
>
> i = [2nd] I (imaginary i) not the letter
> e = [2nd] LN e(x) (natural logarithm)
>
> First I define b as a -70.0 degree polar phasor value; Enter:
>
> define b=e(-70.0i)
>
> Then I try to examine the variable by entering b; the calculator
> returns:
>
> e -25.1576E0i (superscript)
>
> These are not equal.
>
> Calculator Modes:
> Complex format - Polar
> Angle - Degree
> Exact/Approv - Auto
>
> I've tried various combinations of formats and modes and I've discovered
> the following parameters:
>
> Exclusion of the decimal point, b=e(-70i), will store correctly, the
> decimal point seems to confuse it.
>
> Exclusion of i (imaginary) will cause the calculator to return the
> computed value (397.545E-33) which is understandable, although I'd like
> to see the e retained, like pi.
>
> Has anyone seen this before and maybe point me in the right direction?
>
> Thanks,
>
> shamaal@iwl.net
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