import java.applet.Applet;
import java.awt.*;

/**
Program:        MaclaurinSeriesExpansion
Purpose:        sin(x) ‚Ì Maclaurin “WŠJ‚ð•`‚­
@author         segi.tetsu@ss.bch.ntt.jp
@version        1.00; 2 March 1996
*/


public class MaclaurinSeriesExpansion extends Applet {
    final float origin_x = 200;
    final float origin_y = 110;
    final float step_x = 20.0f;
    final float step_y = 20.0f;

    int n = 0;
    int step1, step2, step3, step4, step5, step6; 
    float value[] = new float[61];
    Image image;

    public void init() {
        image = getImage(getDocumentBase(), "images/Sum.gif");

        step1 = Math.round(-3.0f * (float)Math.PI * step_x + origin_x);
        step2 = Math.round(-2.0f * (float)Math.PI * step_x + origin_x);
        step3 = Math.round(-1.0f * (float)Math.PI * step_x + origin_x);
        step4 = Math.round( 1.0f * (float)Math.PI * step_x + origin_x);
        step5 = Math.round( 2.0f * (float)Math.PI * step_x + origin_x);
        step6 = Math.round( 3.0f * (float)Math.PI * step_x + origin_x);
    }

    public void start() {
        for (int i = 0; i < 61; i++)
            value[i] = (float)Math.PI * (float)(i - 30) / 10.0f;
    }

    public void stop() {
        n = 0;
    }

    public void paint(Graphics g) {
        g.drawLine(0, 110, 400, 110);
        g.drawLine(200, 10, 200, 210);
        
        g.drawLine(400, 110, 395, 107);
        g.drawLine(400, 110, 395, 113);
        g.drawLine(200, 10, 197, 15);
        g.drawLine(200, 10, 203, 15);

        g.setFont(new Font("TimesRoman", Font.PLAIN, 15));
        g.drawString("x", 395, 125);
        g.drawString("f(x)", 205, 20);

        g.drawLine(step1, 107, step1, 113);
        g.drawLine(step2, 107, step2, 113);
        g.drawLine(step3, 107, step3, 113);
        g.drawLine(step4, 107, step4, 113);
        g.drawLine(step5, 107, step5, 113);
        g.drawLine(step6, 107, step6, 113);
        g.setFont(new Font("TimesRoman", Font.PLAIN, 10));
        g.drawString("-3PI", step1+2, 108);
        g.drawString("-2PI", step2+2, 118);
        g.drawString("-PI" , step3+2, 108);
        g.drawString("O"   , 202  , 118);
        g.drawString("PI"  , step4+2, 108);
        g.drawString("2PI" , step5+2, 118);
        g.drawString("3PI" , step6+2, 108);

        g.drawLine(197,  30, 203,  30);
        g.drawLine(197,  50, 203,  50);
        g.drawLine(197,  70, 203,  70);
        g.drawLine(197,  90, 203,  90);
        g.drawLine(197, 130, 203, 130);
        g.drawLine(197, 150, 203, 150);
        g.drawLine(197, 170, 203, 170);
        g.drawLine(197, 190, 203, 190);
        g.drawString("4", 205, 33);
        g.drawString("3", 205, 53);
        g.drawString("2", 205, 73);
        g.drawString("1", 205, 93);
        g.drawString("-1", 205, 133);
        g.drawString("-2", 205, 153);
        g.drawString("-3", 205, 173);
        g.drawString("-4", 205, 193);

        g.drawImage(image, 420, 50, this);
        g.setFont(new Font("TimesRoman", Font.ITALIC, 30));
        g.drawString("n="+n, 440, 150);

        for (int i = 0; i < 60; i++) {
            int x1 = Math.round((float)(i - 30) / 10.0f * (float)Math.PI * step_x + origin_x);
            int x2 = Math.round((float)(i - 29) / 10.0f * (float)Math.PI * step_x + origin_x);
            int y1 = Math.round(-value[i] * step_y + origin_y);
            int y2 = Math.round(-value[i + 1] * step_y + origin_y);
            g.drawLine(x1, y1, x2, y2);            
        }        
    }

    public boolean mouseDown(Event e, int x, int y) {
        if (n >= 19)
            return true;

        n++;

        
            int index = 2*n + 1;
            int sign;

            float denominator = 1.0f;
            for (int i = 1; i <= index; i++)
                denominator *= (float)i;

            if ((n % 2) == 0)
                sign = 1;
            else
                sign = -1;

            for (int i = 0; i < 61; i++) {
                float xx = (float)(i - 30) / 10.0f * (float)Math.PI;
                value[i] += (float)sign * (float)Math.pow(xx, index) / denominator;
            }
        
        repaint();
        return true;
    }
}