Java Math calculate angles of a triangle

Question

We would like to calculate angles of a triangle using Java Math class.

We can use the math methods to solve many problems.

Given the three sides of a triangle, for example, we can compute the angles. 


import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    /*from   w  w  w  . j  a v a 2s  .c o  m*/
    // Prompt the user to enter three points
    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();
    
    //your code here
  }
}



import java.util.Scanner;

public class Main {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    
    // Prompt the user to enter three points
    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();
    
    // Compute three sides
    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));
    
    // Compute three angles
    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)));
    
    // Display results
    System.out.println("The three angles are " + 
        Math.round(A * 100) / 100.0 + " " +
        Math.round(B * 100) / 100.0 + " " + 
        Math.round(C * 100) / 100.0);
  }
}



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