HOJ 2016 Conic Distance

#include <stdio.h>
#include <math.h>

double min(double a, double b);

int main()
{
const double pi=acos(-1);
double r, h, d1, a1, d2, a2;
double R, length;//母线和弧长
double theta0, theta, angle;//3D夹角、平面扇形夹角、两给定点与扇形顶点连线夹角
double distance;

while (scanf("%lf %lf %lf %lf %lf %lf", &r, &h, &d1, &a1, &d2, &a2) != EOF)
{
R = sqrt(r * r+h * h);
length = 2 * pi * r;
theta = length / R;
theta0 = fabs(a1-a2);
angle = theta0 * theta / 360.0;
angle = min(angle , theta-angle);
distance = sqrt(d1 * d1 + d2 * d2 - 2 * d1 * d2 * cos(angle) );//余弦定理
printf("%.2lf\n", distance);
}

return 0;
}

double min(double a, double b)
{
if(a > b)
return b;
return a;
}