TI-92 bug
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TI-92 bug
Hi,
I think I may have found a bug in the TI-92 when calculating with
complex numbers in polar format, in degree mode. (No error occurs in
radian mode).
It seems to me that the error occurs because of a bug in the equation
the TI-92 uses when calculating complex numbers in degree mode. However
the equation used by the calc in radian mode is allright.
The following example shows that a wrong result is calculated:
First, in MODE, set the calc to: Angle:DEGREES , Complex format:POLAR ,
Exact/Approx:APPROXIMATE.
Enter the equation: 2*e^35i ( i is the complex constant sqrt(-1) )
Now you get: 2*e^35i = 2*e^-154.65i , which is wrong.
The result should obviously have been the same as entered 2*e^35i (the
calc should not modify it).
Heres a more precise description of why the error occurs:
Set the calc to: Angle:RADIAN , Complex format:RECTANGULAR ,
Exact/Approx:AUTO.
Typing a*e^bi you get a*cos(b)+a*sin(b)i which is right.
(This is right because the calc is in radian mode)
Set the calc to DEGREES:
Typing a*e^bi you get a*cos((180/pi)*b)+a*sin((180/pi)*b)i which is
wrong.
This should have been: a*cos((pi/180)*b)+a*sin((pi/180)*b)i
The error occurs because the equation has 180/pi instead of pi/180 which
it should be.
It would sure be nice to have this little, but serious, bug corrected in
future EPROM upgrades, since I use complex calculating in degree mode a
lot as an electrical engineer.
Some people say that it isn't right to calculate with complex numbers in
degrees and that it should be done in radians. However it works fine on
my HP48 (and all other calcs I have tried).
I would very much like to hear your response on this. Thanks.
Sincerely,
Peter Maigaard
Århus Technical College, Denmark
sm@ciconia.dk
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