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Subject: Re: Fun with calculators
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Sun, 08 Sep 2002 18:17:24 GMT
NNTP-Posting-Date: Sun, 08 Sep 2002 14:17:24 EDT
Organization: Cox Communications
"Chris Carlen" wrote in message
> I recently posted to comp.sys.hp48 a question to see if an HP calculator
> could solve the following differential equation numerically:
> and with the function id(vd)=1E-14*(e^(38.9411*vd)-1). Yes, that is a
> diode current vs. voltage function.
> y[t] in this problem represents the output voltage of a half wave
> rectifier driven by an ideal 10V 50Hz sinewave voltage source into a
> 100uF filter cap and 100 ohm load resistor.
> Anyone have some other interesting underpowered computers they want to
> try to solve this with?
Can't get any more underpowered than a book and a pencil. exp(a*sin(bt)) is
a modified Bessel function, which can be expressed as an infinite sum of
cosine terms. With a little manipulation, you can solve for y in terms of
those modified Bessel functions. If you have a reasonably competent math
function reference, you don't even have to solve for y. If you have Clarke
and Hess, all you have to do is look up the answer.
-- Mike --
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