17 lines
778 B
JavaScript
17 lines
778 B
JavaScript
function det(a, b, c, d, e, f, g, h, i) {
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return a * e * i + b * f * g + c * d * h - a * f * h - b * d * i - c * e * g;
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}
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function circleFromPoints(p1, p2, p3) {
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const a = det(p1.x, p1.y, 1, p2.x, p2.y, 1, p3.x, p3.y, 1);
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const bx = -det(p1.x * p1.x + p1.y * p1.y, p1.y, 1, p2.x * p2.x + p2.y * p2.y, p2.y, 1, p3.x * p3.x + p3.y * p3.y, p3.y, 1);
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const by = det(p1.x * p1.x + p1.y * p1.y, p1.x, 1, p2.x * p2.x + p2.y * p2.y, p2.x, 1, p3.x * p3.x + p3.y * p3.y, p3.x, 1);
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const c = -det(p1.x * p1.x + p1.y * p1.y, p1.x, p1.y, p2.x * p2.x + p2.y * p2.y, p2.x, p2.y, p3.x * p3.x + p3.y * p3.y, p3.x, p3.y);
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return {
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x: -bx / (2 * a),
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y: -by / (2 * a),
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radius: Math.sqrt(bx ** 2 + by ** 2 - 4 * a * c) / (2 * Math.abs(a)),
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};
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}
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