190.cpp

#include <cmath>
#include <cstdio>
#include <cstring>

using namespace std;

int main(void)
{
    double h, k, r, c, d, e;
    double Ax, Ay, Bx, By, Cx, Cy;

    while (scanf("%lf %lf %lf %lf %lf %lf", &Ax, &Ay, &Bx, &By, &Cx, &Cy) != EOF) {
        if (Ay == By) {
            h = (Ax + Bx) / 2;
            k = ((Ax * Ax + Ay * Ay - Cx * Cx - Cy * Cy) / 2 - (Ax - Cx) * h) / (Ay - Cy);
        }
        else if (Ay == Cy) {
            h = (Ax + Cx) / 2;
            k = ((Ax * Ax + Ay * Ay - Bx * Bx - By * By) / 2 - (Ax - Bx) * h) / (Ay - By);
        }
        else {
            h = ((Ax * Ax + Ay * Ay - Bx * Bx - By * By) / (Ay - By) -
                 (Ax * Ax + Ay * Ay - Cx * Cx - Cy * Cy) / (Ay - Cy)) /
                2 / ((Ax - Bx) / (Ay - By) - (Ax - Cx) / (Ay - Cy));
            k = ((Ax * Ax + Ay * Ay - Bx * Bx - By * By) / 2 - (Ax - Bx) * h) / (Ay - By);
        }
        r = sqrt(pow(Ax - h, 2) + pow(Ay - k, 2));

        if (h < 0)
            printf("(x + %.3lf)^2 + ", -(h));
        else if (h > 0)
            printf("(x - %.3lf)^2 + ", h);
        else
            printf("x^2 + ");
        if (k < 0)
            printf("(y + %.3lf)^2 = %.3lf^2\nx^2 + y^2", -(k), r);
        else if (k > 0)
            printf("(y - %.3lf)^2 = %.3lf^2\nx^2 + y^2", k, r);
        else
            printf("y^2 = %.3lf^2\nx^2 + y^2", r);
        if (h < 0)
            printf(" + %.3lfx", h * -2);
        else if (h > 0)
            printf(" - %.3lfx", h * 2);
        if (k < 0)
            printf(" + %.3lfy", k * -2);
        else if (k > 0)
            printf(" - %.3lfy", k * 2);
        e = h * h + k * k - r * r;
        if (e < 0)
            printf(" - %.3lf = 0\n\n", -(e));
        else if (e > 0)
            printf(" + %.3lf = 0\n\n", e);
        else
            printf(" = 0\n\n");
    }

    return 0;
}