Once a number is converted from a floating point number to a rational, the
rational calculations from that point on are done exactly. If you have
algebraic or trigonometric operations, then exact results cannot be
represented in general.
Probably you are not losing precision with ratsubst. You are maintaining
every bit of representation. Your initial input may not warrant such
exactitude.
RJF
> -----Original Message-----
> From: maxima-bounces at math.utexas.edu
> [mailto:maxima-bounces at math.utexas.edu] On Behalf Of amli at comcast.net
> Sent: Friday, September 14, 2007 1:08 PM
> To: maxima at math.utexas.edu
> Subject: Re: [Maxima] Numerical problem
>
> Hello,
>
> Thank you all for responding. I still have a question
> regarding numerical evaluation. This is part of a longer
> symbolic expressions which I am satisfied with. I am not
> just trying to evaluate dot product (which in the case of
> symbolic expression can be verified to show that dot product
> is zero-as shown in the input). When I remove
> keepfloat:true I get very large numbers with exponents 10^.
> I am computing my symbolic expressions for some particular
> cases. Am I losing precision when I see these large numbers
> due to ratsubst . My numbers seems to be very manageable
> from numerical point of view. Can I trust Maxima for
> numerical evaluations to back up my symbolic expresions?
> Thank you.
>
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