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Re: intersection of two circles

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105851] Re: intersection of two circles
  • From: David Skulsky <edskulsky at gmail.com>
  • Date: Tue, 22 Dec 2009 04:03:03 -0500 (EST)
  • References: <hgno39$55l$1@smc.vnet.net>

On Dec 21, 4:01 am, Felix <f.be... at gmx.de> wrote:
> Hey,
> I m already hours busy with trying to find a way to indicate the coordinates of the point(s) where two circles intersect.
> Does Mathematica have a function that gives me the points of intersection if my input are the coordinates (in 2D) and the radii.
> Thanks,
>
> Felix

Perhaps I've misunderstood your question, but you can apply Solve and
NSolve to your problem directly.

For a symbolic answer:

Solve[{(x - x1)^2 + (y - y1)^2 == r1^2, (x - x2)^2 + (y - y2)^2 ==
   r2^2}, {x, y}]

For a numerical answer:

circleIntersect[x1_, y1_, r1_, x2_, y2_, r2_] :=
 NSolve[{(x - x1)^2 + (y - y1)^2 == r1^2, (x - x2)^2 + (y - y2)^2 ==
=
    r2^2}, {x, y}]

David


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