change: use the fact that dot-product of the unit vector is always 1.0

Author: f-frhs

src/Spatial/Euclidean/Circle2D.cs

@@ -168,7 +168,7 @@ private double[] findParameterTs(Line2D line)
             var d = line.Direction;
             var r = this.Radius;
 
-            var a = d.DotProduct(d);
+            var a = 1d;
             var b = 2 * (s.DotProduct(d) - d.DotProduct(cc));
             var c = (s - cc).DotProduct(s - cc) - r * r;