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Re: Numeric warnings during symbolic manipulation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112794] Re: Numeric warnings during symbolic manipulation
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 30 Sep 2010 04:54:17 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

Simplify a and b before use

a = 2/(4 + 1/E^2 + 2 E^2 + E^6) +
    E^2/(4 + 1/E^2 + 2 E^2 + E^6) +
    E^6/(4 + 1/E^2 + 2 E^2 + E^6) //
   Simplify;

b = 4/(4 + 1/E^2 + 2 E^2 + E^6) +
    1/(E^2 (4 + 1/E^2 + 2 E^2 + E^6)) +
    (2 E^2)/(4 + 1/E^2 + 2 E^2 + E^6) +
    E^6/(4 + 1/E^2 + 2 E^2 + E^6) //
   Simplify;

Exp[Log[a/b]] == Exp[Log[a] - Log[b]]

True


Bob Hanlon

---- Yaroslav Bulatov <yaroslavvb at gmail.com> wrote: 

=============
Last two expressions are equivalent. Why does the second one gives
"N::meprec" warnings? Also, is there a good way to stop Mathematica
from running N on my intermediate expressions?

a = 2/(4 + 1/E^2 + 2 E^2 + E^6) + E^2/(4 + 1/E^2 + 2 E^2 + E^6) +
   E^6/(4 + 1/E^2 + 2 E^2 + E^6);
b = 4/(4 + 1/E^2 + 2 E^2 + E^6) + 1/(
   E^2 (4 + 1/E^2 + 2 E^2 + E^6)) + (2 E^2)/(
   4 + 1/E^2 + 2 E^2 + E^6) + E^6/(4 + 1/E^2 + 2 E^2 + E^6);
Exp[Log[a/b]]
Exp[Log[a] - Log[b]]




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