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MathGroup Archive 2004

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Re: Solve bug?

  • To: mathgroup at
  • Subject: [mg52720] Re: [mg52705] Solve bug?
  • From: "David Park" <djmp at>
  • Date: Sat, 11 Dec 2004 05:21:12 -0500 (EST)
  • Sender: owner-wri-mathgroup at


When I solve I get complex numbers for solutions.

Solve[{c1, c2}]
{{x -> 27.25 - 2.621453937237714*I, 
   y -> 53.125 - 19.084184663090557*I}, 
  {x -> 27.25 + 2.621453937237714*I, 
   y -> 53.125 + 19.084184663090557*I}}

And when I plot with ImplicitPlot

ImplicitPlot[{c1, c2}, {x, -30, 70}, {y, 0, 70}]

I get two nonintersecting circles.

David Park
djmp at 

From: paul at [mailto:paul at]
To: mathgroup at

Solve seems to be returning an invalid answer when I do this:

c1 = (-50 + x)^2 + (-50 + y)^2 == 156.25
c2 = (-4.5 + x)^2 + (-56.25 + y)^2 == 156.25

{{x -> 16, y -> 43.75}, {x -> 84, y -> 43.75}}

This answer is so wrong!!??
Those two points are completely off. Not even close.

c1 and c2 are the equations of two overlapping circles.
Use ImplicitPlot to verify this fact.
Why can't Mathematica resolve this simple sytem of equations correctly?

If I am doing something wrong please tell me what it is.

Also how can I cut and paste text from a mathematica notebook without
getting all the slashes?
Your help is greatly appreciated.


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