Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!zephyr.ens.tek.com!orca!pogo!daveb
From: daveb@pogo.WV.TEK.COM (Dave Butler)
Newsgroups: comp.graphics
Subject: Re: Circle algorithms
Message-ID: <7743@pogo.WV.TEK.COM>
Date: 14 Aug 89 20:39:17 GMT
References: <11390021@hpldola.HP.COM>
Reply-To: daveb@pogo.WV.TEK.COM (Dave Butler)
Distribution: na
Organization: Tektronix, Inc., Wilsonville,  OR.
Lines: 26

Just saw the discussion about circles:

Dan Myers writes:

> Jeffrey T LeBlanc writes:
>
>>     Does anyone out there have an algorithm handy that, when given the
>>coordinates of three XY points can return the circle that would fall on
>>them?  Any help along those lines would be appreciated.

Any two points on a circle form a cord of that circle.  A line that is
perpendicular to a cord and bisects that cord also bisects the circle (and
therefore passes through the center of the circle).  Two unique cords, will
have two unique perpendicular bisection lines, both of which pass through the
center of the circle.  Therefore calculate the formula for these lines and
then calculate their intersection point, because that's where the center of
the circle is located. 

				Later,

				Dave Butler

    Why does this magnificent applied science, which saves work and makes 
    life easier, bring us so little happiness? The simple answer runs:
    Because we have not yet learned to make sensible use of it.
				Albert Einstein