已知逆圆弧的起点终点及半径大小，用C++代码求出该逆圆弧的两个圆心

对于逆圆弧，我们可以先将其转化为对应的圆弧，然后再根据圆弧的方法求出两个圆心。具体的做法是，将逆圆弧的起点和终点分别连接圆心，得到两条直径，然后求出这两条直径的交点，即为圆弧的中心点，再根据圆弧的方法求出两个圆心。

代码实现如下：

#include <iostream>
#include <cmath>
using namespace std;

const double PI = acos(-1.0);

int main() {
    double x1, y1, x2, y2, r;
    cin >> x1 >> y1 >> x2 >> y2 >> r;

    // 求出逆圆弧的圆心坐标
    double xm = (x1 + x2) / 2, ym = (y1 + y2) / 2;
    double d = sqrt(r * r - pow(x1 - xm, 2) - pow(y1 - ym, 2));
    double A = atan2(y1 - ym, x1 - xm);
    double B = acos(d / r);
    double C = A + B;
    double D = A - B;
    double xc1 = xm + r * cos(C), yc1 = ym + r * sin(C);
    double xc2 = xm + r * cos(D), yc2 = ym + r * sin(D);

    // 求出圆弧的中心点坐标
    double xa = x1 - xc1, ya = y1 - yc1;
    double xb = x2 - xc1, yb = y2 - yc1;
    double cos_theta = (xa * xb + ya * yb) / (sqrt(xa * xa + ya * ya) * sqrt(xb * xb + yb * yb));
    double sin_theta = sqrt(1 - cos_theta * cos_theta);
    double L = r * acos(cos_theta);
    double xm1 = xc1 + (xa + xb) / 2, ym1 = yc1 + (ya + yb) / 2;
    double u = (xb - xa) / L, v = (ya - yb) / L;
    double xc = xm1 + u * L / 2, yc = ym1 + v * L / 2;

    // 求出圆心坐标
    double d1 = sqrt((x1 - xc) * (x1 - xc) + (y1 - yc) * (y1 - yc));
    double d2 = sqrt((x2 - xc) * (x2 - xc) + (y2 - yc) * (y2 - yc));
    if (abs(d1 - r) < 1e-6) cout << x1 << " " << y1 << " " << xc << " " << yc << endl;
    else if (abs(d2 - r) < 1e-6) cout << x2 << " " << y2 << " " << xc << " " << yc << endl;
    else cout << "No solution" << endl;

    return 0;
}