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FullSimplify issue

  • To: mathgroup at smc.vnet.net
  • Subject: [mg124150] FullSimplify issue
  • From: Tiago <aswedieinparadise at gmail.com>
  • Date: Wed, 11 Jan 2012 04:21:52 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hello,

I want to simplify an expression. FullSimplify does it only if I
include an assumption that has nothing to do with the expression that
I want to simplify. Here is the code:

ListOfAssumptions = {
   b[3] c[1] - b[1] c[3] == 2 Area,
   p[1] + q[1] + 1 == 0,
   p[2] + q[2] + 1 == 0,
   p[3] + q[3] + 1 == 0,
   b[1] + b[2] + b[3] == 0,
   c[1] + c[2] + c[3] == 0,
   (b[1] b[2] + c[1] c[2])/s[1]^2 == p[1],
   (b[2] b[3] + c[2] c[3])/s[2]^2 == p[2],
   (b[3] b[1] + c[3] c[1])/s[3]^2 == p[3],
   (b[1] b[3] + c[1] c[3])/s[1]^2 == q[1],
   (b[2] b[1] + c[2] c[1])/s[2]^2 == q[2],
   (b[3] b[2] + c[3] c[2])/s[3]^2 == q[3],
   (-s[1]^2 - s[2]^2 + s[3]^2)/(2 s[1]^2) == p[1]
   };

FullSimplify[(15 (-2 q[3] s[1]^4 + 4 (1 + q[3]) s[1]^2 s[2]^2 -
      2 (2 + q[3]) s[2]^4 + (s[1]^2 + 3 s[2]^2) s[3]^2 -
      s[3]^4))/(4 (b[3] c[2] - b[2] c[3])^2),
 Assumptions -> ListOfAssumptions]

The result is

30 (1 + q[3])

If I remove from the assumptions list the first assumption (b[3] c[1]
- b[1] c[3] == 2 Area) the result becomes a very large expression.
What should I do in order to not use the assumption b[3] c[1] - b[1]
c[3] == 2 Area ?
(This is important because this is a minimal example from a big set of
expressions).

Thanks,

Carlos Fernandes



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