ComputeAngles.java

import java.util.Scanner;

public class ComputeAngles {

public static void main(String[]args) {

Scanner input = new Scanner(System.in);

System.out.print("Enter three points:  ");

double x1 = input.nextDouble();
double y1 = input.nextDouble();
double x2 = input.nextDouble();
double y2 = input.nextDouble();
double x3 = input.nextDouble();
double y3 = input.nextDouble();

double a = Math.sqrt((x2 - x3) * (x2 - x3)
+ (y2 - y3) * (y2 - y3));

double b = Math.sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3));

double c = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));


double A = Math.toDegrees(Math.acos((a * a - b * b - c * c ) / (-2 * b * c)));

double B = Math.toDegrees(Math.acos((b * b - a * a - c * c)
 / (-2 * a * c)));
double C = Math.toDegrees(Math.acos((c * c - b * b - a * a)
 / (-2 * a * b)));


System.out.println("The three angles are " + Math.round(A * 100) / 100.0);


}

}