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MathGroup Archive 2006

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Re: Finding the periphery of a region

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72005] Re: Finding the periphery of a region
  • From: dh <dh at metrohm.ch>
  • Date: Fri, 8 Dec 2006 06:17:53 -0500 (EST)
  • References: <el8ufm$st3$1@smc.vnet.net>


Hi,

try replacing inequalities by equalities. This should work fine as long 

as you do not have intersecting regions. E.g.:

x^2+y^2<100  ==> x^2+y^2=100, obviously a circle

(5<=x<=25 and -10<=y<=10)  ===>( x==5&&-10<=y<=10) || 

(x==25&&-10<=y<=10) || (5<=x<=25&&y==-10)  || (5<=x<=25&&y==10), four 

line segements.

Daniel



Bonny Banerjee wrote:

> I have a region specified by a logical combination of equatlities and 

> inequalities. For example, r(x,y) is a region defined as follows:

> 

> r(x,y) = x^2+y^2<100 or (5<=x<=25 and -10<=y<=10)

> 

> How do I obtain the periphery of r(x,y)? I am only interested in finite 

> regions i.e. x or y never extends to infinity.

> 

> Thanks,

> Bonny. 

> 

> 



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