Write a program that enables the user to drag the vertices of a triangle and displays the angles dynamically as the triangle shape changes, as shown in Figure 15.30a. The formula to compute angles is given in Listing 4.1.

(a) Exercise enables the user to drag vertices and display the angles dynamically.

Listing

101.93 34.53 43.54 (a) 1 import java.util.Scanner; 2 3 public class ComputeAngles { 4 public static void main(String[] args) { 5 Scanner input = new Scanner (System.in); 6 // Prompt the user to enter three points System.out.print("Enter three points: "); double x1 = input.nextDouble(); double yl = input.nextDouble(); double x2 = input.nextDouble(); double y2 = input.nextDouble(); double x3 = input.nextDouble(); double y3 = input.nextDouble(); 8. 9. 10 11 12 13 14 15 16 17 18 19 20 21 22 // Compute three sides double a = Math.sqrt((x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3)); double b Math.sqrt((x1 - x3) * (x1 - x3) + (yl - y3) * (yl - y3)); double c - + (yl - y2) * (yl - y2)); Math.sqrt((x1 - x2) (1 - 2) 23 // Compute three angles double A = 24 Math.toDegrees (Math.acos ((a / (-2 * b * c))); double B = Math.toDegrees (Math.acos((b / (-2 * a * c))); double C = Math.toDegrees (Math.acos((c * c - b * b - a * a) / (-2 * a * b))); 25 26 27 c) 28 29 30 31 // Display results System.out.println("The three angles are Math.round(A * 100) / 100.0 + " " + 32 33 34 NNNN NNNN NNM mmmm