// The copyright of this program is reserved by �N�L.
/* 
Fourier����
*/ 

/* <applet code="Ex061007b.class" width=360 height=250> </applet> */

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Ex061007b extends JApplet implements ActionListener{
	boolean flag=false;
	double h=0.01;
  JComboBox cb;
  int num = 1;
  String cbl[]={"n=1","n=2","n=3","n=4","n=5","n=6","n=7","n=8","n=9","n=10","n=11","n=12","n=13","n=14","n=15","n=16","n=17","n=18","n=19","n=20","n=21","n=22","n=23","n=24","n=25","n=26","n=27","n=28","n=29","n=30","n=31","n=32","n=33","n=34","n=35","n=36","n=37","n=38","n=39","n=40"};
  public void init(){
		Container cp =getContentPane();
		JPanel pl = new JPanel();
		pl.setBackground(Color.black);
    cb = new JComboBox(cbl);
    cb.setBounds(0,0,60,20);
    cb.setSelectedIndex(0);
    cb.addActionListener(this);
		pl.setLayout(null);
		pl.add(cb);
		cp.add(pl);		
	}

  public void actionPerformed(ActionEvent event){
		num = cb.getSelectedIndex()+1; 
		flag=true;
		repaint();
	}
	
	public void paint(Graphics g){
		super.paint(g);
		g.setColor(Color.blue);
		g.drawLine(23,125,337,125);
		g.drawLine(180,25,180,225);
		g.drawRect(23,25,314,200);
		g.setColor(Color.red);
		g.drawString("-��",8,125);
		g.drawString("��",340,125);
		if(flag==true)
			for(double x=-Math.PI;x<Math.PI;x+=h){
		  	g.setColor(Color.green);
	 	  	g.drawLine((int)(x*50+180),125-(int)(Fourier(num,x)*100),(int)((x+h)*50+180),125-(int)(Fourier(num,x+h)*100));
			}	
	}		

  // Fourier����
	public double Fourier(int n, double x){
		double val=0.0;
		for(int i=1;i<=n;i++)
			val+=Math.sin((2.0*i-1.0)*x)/(2.0*i-1.0);
		return(4.0*val/Math.PI);
	}
}