/**
* Calculate angle of tangent line at a particular point
*
* @param t : parameter
* @return angle
*/
public double calcDirectionAt(double t) {
final boolean db = false;
calcTangentAt(t, workPt);
double a = Math.atan2(workPt.y, workPt.x);
if (db) {
System.out.println("calcDirectionAt " + Tools.f(t) + " a=" + Tools.fa(a));
}
return a;
}
