Code mẫu

#include <bits/stdc++.h>
#define ld long double
using namespace std;
ld pi=3.1415926535897932384626433;
int test;
ld r1,r2,al,x,rr,beta,beta1,haf,s,res;
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    freopen("GEOMETRY.INP","r",stdin);
    freopen("GEOMETRY.OUT","w",stdout);
    cin>>test;
    while(test--){
        cin>>r1>>r2;
        al=atan((r1+r2)/r1);
        x=2.0000*r1*cos(al);
        rr=r1*r1;
        beta=acos((2.000*rr-x*x)/(2.000*rr));
        beta1=pi/2.000-beta;
        haf=(r1+r1+x)/2.000;
        s=sqrt(haf*(haf-r1)*(haf-r1)*(haf-x));
        res=r1*(r1+r2)-s-beta1*rr-(pi/2.000-al)*r2*r2;
    res=res/2.000;
        cout<<setprecision(4)<<fixed<<res<<'\n';
    }
}