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. > >

**Follow-Ups**:**Re: Re: Finding the periphery of a region***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>