Plot the sine and cosine functions

Question

I'm currently having some problems regarding my homework.

Here's the Exercise:

(Plot the sine and cosine functions) Write a program that plots the sine function in red and the cosine function in blue.

hint: The Unicode for Pi is \u03c0. To display -2Pi, use g.drawString("-2\u03c0", x, y). For a trigonometric function like sin(x), x is in radians. Use the following loop to add the points to a polygon p

for (int x = -170; x <= 170; x++) {
    p.addPoint(x + 200, 100 - (int)(50 * Math.sin((x / 100.0) * 2 * Math.PI)));

-2Pi is at (100, 100), the center of the axis is at (200, 100), and 2Pi is at (300, 100) Use the drawPolyline method in the Graphics class to connect the points.

Okay, so the sin function I have is a little different from the one in the exercise but it works so it shouldn't be a problem. The cosine function on the other hand, I'm having trouble finding the code for it so I don't have that in my program.

What I also need to do is place -Pi and Pi on the graph on their respectable places.

So, here's the code.

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Polygon;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Exercise13_12 extends JFrame {

public Exercise13_12() {
    setLayout(new BorderLayout());
    add(new DrawSine(), BorderLayout.CENTER);
}

public static void main(String[] args) {
    Exercise13_12 frame = new Exercise13_12();
    frame.setSize(400, 300);
    frame.setTitle("Exercise13_12");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);

}

class DrawSine extends JPanel {

    double f(double x) {
        return Math.sin(x);
    }

    double g(double y) {
        return Math.cos(y);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        g.drawLine(10, 100, 380, 100);
        g.drawLine(200, 30, 200, 190);

        g.drawLine(380, 100, 370, 90);
        g.drawLine(380, 100, 370, 110);
        g.drawLine(200, 30, 190, 40);
        g.drawLine(200, 30, 210, 40);

        g.drawString("X", 360, 80);
        g.drawString("Y", 220, 40);

        Polygon p = new Polygon();

        for (int x = -170; x <= 170; x++) {
            p.addPoint(x + 200, 100 - (int) (50 * f((x / 100.0) * 2
                    * Math.PI)));

        }

        g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
        g.drawString("-2\u03c0", 95, 115);
        g.drawString("2\u03c0", 305, 115);
        g.drawString("0", 200, 115);
    }
 }
}

If anyone have the time to help me out I would be very grateful.

Answer 1

Try this:

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.Color;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Exercise13_12 extends JFrame {

public Exercise13_12() {
    setLayout(new BorderLayout());
    add(new DrawSine(), BorderLayout.CENTER);
}

public static void main(String[] args) {
    Exercise13_12 frame = new Exercise13_12();
    frame.setSize(400, 300);
    frame.setTitle("Exercise13_12");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true);

}

class DrawSine extends JPanel {

    double f(double x) {
        return Math.sin(x);
    }

    double gCos(double y) {
        return Math.cos(y);
    }

    protected void paintComponent(Graphics g) 
    {
        super.paintComponent(g);

        g.drawLine(10, 100, 380, 100);
        g.drawLine(200, 30, 200, 190);

        g.drawLine(380, 100, 370, 90);
        g.drawLine(380, 100, 370, 110);
        g.drawLine(200, 30, 190, 40);
        g.drawLine(200, 30, 210, 40);

        g.drawString("X", 360, 80);
        g.drawString("Y", 220, 40);

        Polygon p = new Polygon();
        Polygon p2 = new Polygon();

       for (int x = -170; x <= 170; x++) {
            p.addPoint(x + 200, 100 - (int) (50 * f((x / 100.0) * 2
                    * Math.PI)));

        }

        for (int x = -170; x <= 170; x++) {
            p2.addPoint(x + 200, 100 - (int) (50 * gCos((x / 100.0) * 2
                    * Math.PI)));

        }

        g.setColor(Color.red);
        g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
        g.drawString("-2\u03c0", 95, 115);
        g.drawString("2\u03c0", 305, 115);
        g.drawString("0", 200, 115);

        g.setColor(Color.blue);
        g.drawPolyline(p2.xpoints, p2.ypoints, p2.npoints);

    }
 }
}

Basically it's the same code all over, but you need a new polygon to draw it. And then I set the color using the setColor() function of the Graphics.