/*
 * h3b.java - revised 18 Apr 05 - width 401, height 71
 * @author jackord@kw.igs.net
 */

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class h3b extends Applet 
                   implements ActionListener {
  String bs = "Run";                              
  Button b = new Button(bs);
  int k=0;

  public void init() {
    setLayout(new FlowLayout(FlowLayout.LEFT));
    setBackground(new Color(211, 211, 211));
    add(b);
    b.addActionListener(this);
  }

  public void paint(Graphics g) {
    g.drawRect(0, 0, 400, 70);
    if (k==1) {
      double gr, l, s, sm, ds, t, v1, v2, dt, v, a;
      int n=400;
      gr=9.8; l=9.8; sm=l*Math.PI/2; ds=2*sm/n;
      t=0; v1=0;
      for (int i=1; i<=n-1; i=i+1) {
        s=sm-i*ds; v2=Math.sqrt(2*gr*l*(Math.cos(s/l)-Math.cos(sm/l)));
        t=t+2/(v1+v2); v1=v2;
      }
      t=2*(t+2/v1)*ds;
      g.drawString("90 deg amplitude Tvbar = "+(float)t, 100, 20);

      dt=.01;
      t=0; s=sm; v=0; a=-gr*Math.sin(s/l);
      v=v+a*dt/2;
      do {
        t=t+dt; s=s+v*dt; a=-gr*Math.sin(s/l); v=v+a*dt;
      } while (v<0);
      t=2*(t+dt/2-v/a);
      g.drawString("90 deg amplitude Tfeyn = "+(float)t, 100, 40);
      t=t/2/Math.PI-1;
      g.drawString("Increase over small angle T = "+((int)(1000*t))/10+" %", 100, 60);
    }
  }

  public void actionPerformed(ActionEvent e) {
    String tst;
    tst=e.getActionCommand();
    if (bs.equals(tst)) { k=1; }
    repaint();
  }
}