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MathGroup Archive 2005

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Re: odd mathematica blindspot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56502] Re: odd mathematica blindspot
  • From: Skirmantas <skirmantas.janusonis at yale.edu>
  • Date: Tue, 26 Apr 2005 21:53:49 -0400 (EDT)
  • References: <d4klbs$eg7$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi Ed,

By definition, 9999999999999/10000000000000 is an exact rational number, whereas 0.5 is an approximate real number:

In[2]:=
0.5===1/2

Out[2]=
False

In[9]:=
9999999999/10000000000===0.9999999999

Out[9]=
False

In[10]:=
9999999999./10000000000===0.9999999999

Out[10]=
True

So:

In[11]:=Solve[(9999999999999/10000000000000)^x == .5, x]
Out[11]={}

In[12]:=Solve[(9999999999999./10000000000000)^x == .5, x]
Out[12]={{x -> 6.937016409072274`*^12}}

Skirmantas


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