ellipse(椭圆截面积).cpp

杭电acm解题报告2001---2099.

#include<cstdio>
#include<cmath>
#define PI 3.14159265
double a,b,l,r;
double f(double t)
{
    return t/2 - sin(2*t)/4;
}
double solve()
{
    double ans,sin2l,sin2r,tal,tar;
    
    tal = acos( l/a );
    tar = acos( r/a );

    ans = -2 * a * b * ( f(tar) - f(tal) );

    return ans;
}
int main()
{
    int n;
    //printf("%lf\n",acos(-1));
    scanf("%d",&n);
    while(n--)
    {
        scanf("%lf %lf %lf %lf",&a,&b,&l,&r);
        printf("%.3lf\n",solve());
    }
}