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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Fun with C
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Date: Thu, 28 Apr 2011 15:56:56 +0200
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Date: 2011-04-28T15:56:52+02:00
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On Thu, 28 Apr 2011 06:24:45 -0400, Peter C. Chapin wrote:

> On Thu, 28 Apr 2011 09:41:51 +0200, "Dmitry A. Kazakov"
> <mailbox@dmitry-kazakov.de> wrote:
> 
>>> The above equation does not define the spring mechanics.
>>
>>It is not an equation, it is a solution of some second-order differential
>>equation [equations themselves can be linear or not, which is unrelated to
>>the issue].
> 
> It's not unrelated to the issue at all. A system is called a "linear
> system" because it is described by a linear differential equation. That's a
> matter of definitition.

Not really. Your definition is derived from this one:

http://en.wikipedia.org/wiki/Linear_system

which is applied to an open system with an input and output.

I meant a closed system, which motion is described by a linear function of
time. The definition above cannot applied to a close system, only to some
parts of.

Nobody so far argued that sine is a linear function because it is a
solution of a linear differential equation. OK, let it be linear, my point
is that it still would be inappropriate to use linear x instead of "linear"
sin(x) to describe motion of a pendulum.

[This reminds me "fruitful" discussions about "arrays" of C. Why should it
always end this way?]

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de