Centre and radius of a circle passing through 3 points in a plane: Difference between revisions
Centre and radius of a circle passing through 3 points in a plane (view source)
Revision as of 21:47, 20 February 2024
, 4 months agoAdded Wren
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<pre>
Centre = 18.97851566, 16.2654108, radius = 7.354312
</pre>
=={{header|Wren}}==
This follows the lines of the C++ code [https://www.geeksforgeeks.org/equation-of-circle-when-three-points-on-the-circle-are-given/ here].
I've used [22.83, 2.07] for the first point, rather than [22.82, 2.07] as stated in the task description, to give agreement on the centre with the F# and Phix examples. However, my radius is twice theirs and looks right to me.
<syntaxhighlight lang="wren">var findCircle = Fn.new { |x1, y1, x2, y2, x3, y3|
var x12 = x1 - x2
var x13 = x1 - x3
var y12 = y1 - y2
var y13 = y1 - y3
var y31 = y3 - y1
var y21 = y2 - y1
var x31 = x3 - x1
var x21 = x2 - x1
var sx13 = x1 * x1 - x3 * x3
var sy13 = y1 * y1 - y3 * y3
var sx21 = x2 * x2 - x1 * x1
var sy21 = y2 * y2 - y1 * y1
var f = sx13 * x12 + sy13 * x12 + sx21 * x13 + sy21 * x13
f = f / (y31 * x12 - y21 * x13) / 2
var g = sx13 * y12 + sy13 * y12 + sx21 * y13 + sy21 * y13
g = g / (x31 * y12 - x21 * y13) / 2
var c = -x1 * x1 - y1 * y1 - 2 * g * x1 - 2 * f * y1
var h = -g
var k = -f
var r = (h * h + k * k - c).sqrt
return [h, k, r]
}
var hkr = findCircle.call(22.83, 2.07, 14.39, 30.24, 33.65, 17.31)
System.print("Centre is at %([hkr[0], hkr[1]])")
System.print("Radius is %(hkr[2])")
System.print("\nCheck radius as the distance between the centre and the first point:")
System.print(((22.83 - hkr[0]).pow(2) + (2.07 - hkr[1]).pow(2)).sqrt)</syntaxhighlight>
{{out}}
<pre>
Centre is at [18.978515660149, 16.265410797716]
Radius is 14.708623978334
Check radius as the distance between the centre and the first point:
14.708623978334
</pre>
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