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Subject: Re: Parallel to line through point without slope calculation
Date: Thu, 28 Mar 2013 15:18:06 +0000 (UTC)
Organization: University of Toronto
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"Roger Stafford" wrote in message <kj0pkf$o9r$1@newscl01ah.mathworks.com>...
> "K" wrote in message <kivmba$jnh$1@newscl01ah.mathworks.com>...
> > I have two points (a,b) that make up a line, and a third point (c). I'd like to draw a line (length x) that is parallel to (a,b) but passes through c (at its midpoint).
> - - - - - - - - -
>   Let a, b, and c be vectors of the three given points, each consisting of their respective cartesian coordinates.  The two vectors, d and e, of the endpoints of the desired line segment parallel to the line through a and b with c as its midpoint and of length x can be calculated as follows:
> 
>  t = x/2*(b-a)/norm(b-a);
>  d = c + t;
>  e = c - t;
> 
> No slope computation is involved.
> 
> Roger Stafford

This is magnificent! Thank you so very much, Mr. Stafford.