A complex cone

#include<iostream>
#include<cmath>

int main()
{
    int t;
    scanf("%d", &t);

    while(t--)
    {
        int r, h, a, b;
        scanf("%d%d%d%d", &r, &h, &a, &b);
        double delta = 1e-5;
        double area = 0.0;
        double y = 0.0;
        double volumeIntersect = 0.0;
        do
        {
            double c = (y * (a+b)) /(2*r*(h-y));
            double d = (r - r * y / h);
            double e = 2 * std::acos(c) * d * d;
            double f = y * (a+b) / (2*h);
            double g = std::sqrt(d * d - f * f) * y * (a+b) / h;
            area = (e - g);
            volumeIntersect += area * delta;
            y += delta;
        } while (area - delta > 0);
        double volume = 2.0 * h * r * r * M_PI / 3.0;

        printf("%f\n",volume - volumeIntersect);
    }

    return 0;
}