圆上的三个随机点
圆上的三个随机点
提问于 2016-01-12 00:02:15
我正在尝试创建一个程序，其中一个圆中的三个随机点被创建，并导致创建一个内接三角形。然而，我得到的角度都搞砸了
下面是我的代码：
public static void main(String[] args) {
double r = 40.0;
double angle1 = Math.random()* (2 * Math.PI);
double angle2 = Math.random()* (2 * Math.PI);
double angle3 = Math.random()* (2 * Math.PI);
double x_1 = r * Math.cos(angle1);
double y_1 = r * Math.sin(angle1);
double x_2 = r * Math.cos(angle2);
double y_2 = r * Math.sin(angle2);
double x_3 = r * Math.cos(angle3);
double y_3 = r * Math.sin(angle3);
System.out.println("The coordinates of the three points are:
(" + x_1 + ", " + y_1 + ")
(" + x_2 + ", " + y_2 + ")
(" + x_3 + ", " + y_3 + ")");
//Get length of each side
double distanceFrom1To2 = Math.sqrt(Math.pow(x_2 - x_1, 2) +
Math.pow(y_2 - y_1, 2));
double distanceFrom2To3 = Math.sqrt(Math.pow(x_3 - x_2, 2) +
Math.pow(y_3 - y_2, 2));
double distanceFrom3To1 = Math.sqrt(Math.pow(x_1 - x_3, 2) +
Math.pow(y_1 - y_3, 2));
//Get angles ***
double triangleAngle1 = Math.atan(distanceFrom1To2 / distanceFrom2To3);
double triangleAngle2 = Math.atan(distanceFrom2To3 / distanceFrom3To1);
double triangleAngle3 = Math.atan(distanceFrom3To1 / distanceFrom1To2);
System.out.println("The three angles are " + triangleAngle1 + " " +
triangleAngle2 + " " + triangleAngle3);
System.out.println(triangleAngle1 + triangleAngle2 + triangleAngle3);
}我绝对知道获取角度的方法都搞砸了。下面是我的程序的运行示例：
The coordinates of the three points are: (5.224534224725408,
-39.65733528787168) (-29.696946087404676, 26.79722733944279)
(32.70889681040468, -23.02451018906371)
The three angles are 0.7545364726122026 1.18830825410364
0.40435068059871415
Total angle sum: 2.347195407314557所有角度加起来都比Pi /2弧度大得多。我考虑过正弦定律，但你至少要知道一个角度...
Stack Overflow用户
发布于 2016-01-12 01:20:32
弄清楚了
下面是固定的代码：
//Get length of each side
double a = Math.sqrt(Math.pow(x_2 - x_1, 2) + Math.pow(y_2 - y_1, 2)); // distance from 1 to 2
double b = Math.sqrt(Math.pow(x_3 - x_2, 2) + Math.pow(y_3 - y_2, 2)); // distance from 2 to 3
double c = Math.sqrt(Math.pow(x_1 - x_3, 2) + Math.pow(y_1 - y_3, 2)); // distance from 3 to 1
//Get angles ***
double triangleAngle1 = Math.acos((Math.pow(a, 2) + Math.pow(b, 2) - Math.pow(c, 2)) / (2 * a * b));
double triangleAngle2 = Math.acos((Math.pow(b, 2) + Math.pow(c, 2) - Math.pow(a, 2)) / (2 * c * b));
double triangleAngle3 = Math.acos((Math.pow(c, 2) + Math.pow(a, 2) - Math.pow(b, 2)) / (2 * a * c));我把它改成用余弦定律。
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原文链接：
https://stackoverflow.com/questions/34725929
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