怎么求 Java 贝塞尔曲线两点之间的角度

public void test() {
CvPoint controlPoint[] = new CvPoint[4];
controlPoint[0] = new CvPoint(50, 60); //起点
controlPoint[1] = new CvPoint(130, 200); //控制点
controlPoint[2] = new CvPoint(300, 360); //控制点
controlPoint[3] = new CvPoint(400, 600); //终点
int n = controlPoint.length - 1; //
int i, r;
float u;

bezierPoint.clear();
// u的步长决定了曲线点的精度
for (u = 0; u <= 1; u += 0.01) {

CvPoint p[] = new CvPoint[n + 1];
for (i = 0; i <= n; i++) {
p[i] = new CvPoint(controlPoint[i].x, controlPoint[i].y);
}

for (r = 1; r <= n; r++) {
for (i = 0; i <= n - r; i++) {
p[i].x = (1 - u) * p[i].x + u * p[i + 1].x;
p[i].y = (1 - u) * p[i].y + u * p[i + 1].y;
}
}
bezierPoint.add(p[0]);
}

for (CvPoint point : bezierPoint) {
System.out.println(point.x + "," + point.y);
}
}