[Date Index]
[Thread Index]
[Author Index]
Re: Problem with FullSimplify in Version 5: Rationals are converted to Reals
*To*: mathgroup at smc.vnet.net
*Subject*: [mg45518] Re: Problem with FullSimplify in Version 5: Rationals are converted to Reals
*From*: drbob at bigfoot.com (Bobby R. Treat)
*Date*: Sun, 11 Jan 2004 03:20:20 -0500 (EST)
*References*: <bto17c$2gp$1@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
Version 5.0's is the correct behavior, in my opinion. Either we have
unlimited precision, or we don't. In your expression, we don't--and
the result of FullSimplify is, indeed, simpler after recognizing the
fact.
Bobby
oberfeld <oberfeld at uni-mainz.de> wrote in message news:<bto17c$2gp$1 at smc.vnet.net>...
> Dear list,
>
> while trying to solve an equation that could be solved without problems
> in MA 4.2, Solve[] does not find a solution in Ma 5.0.0.0.
>
> I found that the problem is due to FullSimplify[] in Version 5.
>
> In Version 4.2,
> Full Simplify[
> Erf [
> (
> -(Log[10000000000]/Log[10]) -
> Log[10^(-12 + (20 +deltaL)/10)]/Log[10]
> )/
> (Sqrt[2]*Sqrt[0.25302502757884177 +
> (0.6089140226261116 - 0.005294904544574884*
> (20 + deltaL))2])
> ]
> ]
>
> yields
>
> Out:=-Erf[Log[10^(deltaL/10)]/
> (Sqrt[1.012100110315367 + (-0.010653685371740707 +
> 0.00005607202827231952*deltaL)*deltaL]*Log[10])]
>
> In Version 5, I get
>
> Out:=0.5 - 0.25*Erf[(0. -
> 0.30709257318568767*Log[E^(0.2302585092994046*deltaL)])/
> Sqrt[0.5060500551576835 + (-0.005326842685870354 +
> 0.00002803601413615976*deltaL)*
> deltaL]] +
> 0.25*Erf[(0. + 0.30709257318568767*Log[E^(0.2302585092994046*deltaL)])/
> Sqrt[0.5060500551576835 + (-0.005326842685870354 +
> 0.00002803601413615976*deltaL)*
> deltaL]]
>
> So, FullSimplify[] in Version 5 has obviously converted *all numbers* to
> Reals, while in Version 4.2, Rationals are used where available!!
>
> As a consequence, Solve[] Version 5 can not find a solution to an
> equation in which the above term appears.
>
> QUESTION: do you know of a fix available for FullSimplify[] in Version 5
> that corrects for this behaviour?
> Or are there any Options which can be used to 'reset' FullSimplify[] in
> Version 5 to the behavior of Version 4.2??
>
>
> Best wishes,
>
> Daniel Oberfeld-Twistel
>
> ----------------------------
> Daniel Oberfeld-Twistel
> Institute of Psychology
> Experimental Psychology
> University of Mainz
> Staudingerweg 9
> 55099 Mainz
> Germany
Prev by Date:
**Re: Compile**
Next by Date:
**Re: functions**
Previous by thread:
**Re: Problem with FullSimplify in Version 5: Rationals are converted to Reals**
Next by thread:
**fonts**
| |