Exercise04_02.java

package Ch_04;

/* 4.2 (Geometry: great circle distance) The great circle distance is the
 *  distance between two points on the surface of a sphere. Let (x1, y1) 
 *  and (x2, y2) be the geographical latitude and longitude of two points. 
 *  The great circle distance between the two points can be computed using 
 *  the following formula:
 * Write a program that prompts the user to enter the latitude and
 * longitude of two points on the earth in degrees and displays its great 
 * circle distance. The average earth radius is 6,371.01 km. Note that you 
 * need to convert the degrees into radians using the Math.toRadians method 
 * since the Java trigonometric methods use radians. The latitude and 
 * longitude degrees in the formula are for north and west. Use negative to
 * indicate south and east degrees. 
*/
import java.util.Scanner;

public class Exercise04_02 {
	public static void main(String[] args) {
		
		double xOne,xTwo,yOne,yTwo,distance;
		
		final double radius = 6371.01;
		
		Scanner input = new Scanner(System.in);
		
		System.out.println("Enter point 1 (latitude and longitude) in degrees: ");
		
		xOne = input.nextDouble();
		yOne = input.nextDouble();
		
		xOne = Math.toRadians(xOne);
		yOne = Math.toRadians(yOne);
		
		System.out.println("Enter point 2 (latitude and longitude) in degrees: ");
		
		xTwo = input.nextDouble();
		yTwo = input.nextDouble();
		
		xTwo = Math.toRadians(xTwo);
		yTwo = Math.toRadians(yTwo);
		
		
		
		distance = radius * (Math.acos((Math.sin(xOne) * Math.sin(xTwo)) +
				(Math.cos(xOne) * Math.cos(xTwo) * Math.cos(yOne - yTwo))));
		
		System.out.println("The distance between the two points is: " + distance
				+ " km" );
		
		
		
		
		
		
		
		
		
		
		
		
		
	}

}