Calculating Angles

Here is an example of how one might use Java to accomplish this task:

import java.lang.*;
import java.io.*;
import java.awt.geom.*;

public class Angles  {

  public static void main(String[] args) {
    
    Point2D.Double p1 = new Point2D.Double(2,0);
    Point2D.Double p2 = new Point2D.Double(4,0);
    Point2D.Double p3 = new Point2D.Double(4,4);
    
    Arc2D.Double arc = new Arc2D.Double();
    
    arc.setArcByTangent(p1,p2,p3,1);
    
    System.out.println( arc.getAngleExtent() );
  }
  
}