Java

Java：在一个已知原点半径的圆上随机产生三个点构成三角形，求三角形的三个角度。

public class RandomPointsOnACircle {

public static void main(String[] args) {
	// TODO Auto-generated method stub
	double x0 = 0;
	double y0 = 0;
	final int RADIUS = 40;
	
	double angleInRadians1 = Math.random() * Math.PI * 2;
	double angleInRadians2 = Math.random() * Math.PI * 2;
	double angleInRadians3 = Math.random() * Math.PI * 2;
	int x1 = (int) (x0 + RADIUS * Math.cos(angleInRadians1));
	int y1 = (int) (y0 + RADIUS * Math.sin(angleInRadians1));
	int x2 = (int) (x0 + RADIUS * Math.cos(angleInRadians2));
	int y2 = (int) (y0 + RADIUS * Math.sin(angleInRadians2));
	int x3 = (int) (x0 + RADIUS * Math.cos(angleInRadians3));
	int y3 = (int) (x0 + RADIUS * Math.sin(angleInRadians3));
	
	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));
	System.out.println(a);
	
	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 - a * a - b * b) / (-2 * a * b)));
	
	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);
}

}