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MathGroup Archive 2006

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Solve chokes on Piecewise input that Reduce handles quite well??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72007] Solve chokes on Piecewise input that Reduce handles quite well??
  • From: "Chris Chiasson" <chris at chiasson.name>
  • Date: Fri, 8 Dec 2006 06:17:55 -0500 (EST)

Solve[{0 == Piecewise[{{1/(-1 + X[1] + X[2])^2, X[1] + X[2] <= -1}},
(1/2)*(3/2 + (1/2)*(-1 + X[1] + X[2]))] +
     Piecewise[{{(1/2)*(-(3/2) + X[1]/2), X[1] < 2}, {-(1/4), X[1] ==
2}}, -(1/X[1]^2)] + 2*(-1 + X[1]),
   0 == Piecewise[{{1/(-1 + X[1] + X[2])^2, X[1] + X[2] <= -1}},
(1/2)*(3/2 + (1/2)*(-1 + X[1] + X[2]))] +
     2*(-1 + X[2])}, {X[1], X[2]}]

Solve::eqf: X[1]+X[2]\[LessEqual]-1 is not a well-formed equation.

...

(and it returns the input)

Here is the same command using Reduce:

Reduce[{0 == Piecewise[{{1/(-1 + X[1] + X[2])^2, X[1] + X[2] <= -1}},
(1/2)*(3/2 + (1/2)*(-1 + X[1] + X[2]))] +Piecewise[{{(1/2)*(-(3/2) +
X[1]/2), X[1] < 2}, {-(1/4), X[1] == 2}}, -(1/X[1]^2)] + 2*(-1 +
X[1]),
   0 == Piecewise[{{1/(-1 + X[1] + X[2])^2, X[1] + X[2] <= -1}},
(1/2)*(3/2 + (1/2)*(-1 + X[1] + X[2]))] +
     2*(-1 + X[2])}, {X[1], X[2]}]

X[1] == 75/89 && X[2] == 51/89

Did I do anything wrong? Is this a bug? If it is a bug, please file it
and fix it.

-- 
http://chris.chiasson.name/


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