Circle through three points.xls



Let the three given points be a, b, c. Use ax and ay to represent the x and y coordinates of a, and so on. The coordinates of the center p=(px,py) of the circle determined by a, b, and c are:


Calculation Reference

Submitted On:
11 Feb 2008
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Comments: 2
JohnDoyle[Admin] 15 years ago
You are quite right xmarks102. I noticed two incorrect formulas. I have corrected them and updated the file to version 1.2 - your problem works fine now. Thanks for the comment!
JohnDoyle[Admin] 15 years ago
To try this out I used a unit circle and put in points (-1,0), (0,1) and (1,0). I should get a center of (0,0) and a raduis of 1, right? Instead I get a center of (-.5,-.5) and a radius of 0.707. I'm no math whiz, but this makes no sense to me. I moved the third point around the circle 30 degrees to (.866, .5) and then got a center of (-.2255, -.7745) and a radius of 1.095.