From: Chris <behmc@...>

Date: Thu, 11 Dec 1997 09:08:59 -0500

Date: Thu, 11 Dec 1997 09:08:59 -0500

>Does anyone know the answer to these two geometry questions? > > >1. The formula for finding the intersection point of two lines. > >2. Given the coordinates of three points that lie on the arc of a circle, >how do you find the radius and centre of that circle. > >I have the source code for the first in C, but of course it is complete >gibberish. Even the basic maths formula is complete gibberish, and cannot >be written in ASCII... at least by me. > >Its not really my excuse that I am Australian, lazy and or thick although >any or all of these may be true. Also I have no control over Lazlo Toth >or what he says. > >JC The intersection point of two lines is found by setting the two line equations equal to each other, solving for x and then substituting that value into one of the original equations to find y. Example: y1 = 3x + 2 y2 = -4x Find x where they intersect 3x + 2 = -4x 2 = -7x -2/7 = x So at the x coordinate -2/7 the lines will intersect. y1 = 3x + 2 y1 = 3(-2/7) + 2 y1 = -6/7 + 2 y1 = 8/7 So the point where they cross is (-2/7,8/7). I haven't ever tried (or wanted to try) to do the actual formula in BASIC (or any language) so I won't attempt it here - hopefully though you can see what needs to be done (and maybe how to convert it from C) by this example. HTH, *Chris