Re: strange problem

[Geraint Paul Bevan]

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Gerald Ebberink wrote:

| I get this result
|
| ans =
|
|    -2.0817e-17    1.0000e+02
|    -1.0000e-02    1.0000e+00
|


| so how does this strange number gets up there?
|
| and even better is there a solution because this gives me a unworkable
| solution in the end.
|

The number -2.0817e-17 is -0.000000000000000020817, which is very, very
close to zero. The error is due to the way that numbers are represented
in computers. You can learn more about floating point arithmetic, which
is the cause of the error, in the paper "What Every Computer Scientist
Should Know About Floating Point Arithmetic (1991)" which is available
on line at:

http://citeseer.nj.nec.com/goldberg91what.html

There are some tools available which work to arbitrary precision,
however, if your calculations rely on exact representation, you should
probably change your algorithms - they are not well suited to use on a
digital computer.

- --
Geraint Bevan
http://homepage.ntlworld.com/geraint.bevan

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