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MathGroup Archive 2005

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Re: odd mathematica blindspot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56484] Re: [mg56468] odd mathematica blindspot
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 26 Apr 2005 21:52:39 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

$Version

5.1 for Mac OS X (January 27, 2005)

Off[Solve::ifun];

x/.(Solve[(999999999999/10000000000000)^x\[Equal].5,x]//Flatten)

0.30103

x /. (Solve[(999999999999/10000000000000)^x\[Equal]1/2,x]//Flatten)

Log[2]/Log[10000000000000/999999999999]

%//N

0.30103


Bob Hanlon

> 
> From: Edward Peschko <esp5 at pge.com>
To: mathgroup at smc.vnet.net
> Date: 2005/04/26 Tue AM 01:33:53 EDT
> Subject: [mg56484] [mg56468] odd mathematica blindspot
> 
> hey all,
> 
> I was wondering why the following didn't output any solutions. I'd think 
> it would be easy:
> 
> 	Solve[(999999999999/10000000000000)^x == .5, x]
> 
> It gives no solutions. What's really odd is when you say:
> 
> 	Solve[(999/1000)^x==.5, x]
> 
> which *does* give solutions, in the form:
> 
> 	{{x -> 692.801... }}
> 
> Also, just curious, but how do you extract 'x' from the above? 
> Say I wanted to plug the above solution into another equation.. 
> In perl I'd say something like:
> 
> y = Solve[(999/1000)^x == .5, x];
> 
> 3 * y->{x}  # replaces with 692.81
> 
> etc. etc.
> 
> but this doesn't seem to work. How do you access parts of a mathematica
> datastructure/hash?
> 
> And finally, how do you set values with the tty? ie: suppose my backspace 
and
> delete key aren't working with math.exe (they aren't) and I want them to
> delete typos. In unix this would be stty erase ^H. In mathematica...?
> 
> Thanks much for any help,
> 
> Ed
> 
> 


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