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| #include <bits/stdc++.h>
using namespace std;
typedef long double ld;
const ld IR2=100;
const ld PI=3.141592653589793238462643383279502884197169399375105820974944592307816L;
struct Point {
ld x,y;
Point(ld _x=0,ld _y=0):x(_x),y(_y) {}
Point operator +(const Point &R) {
return Point(R.x+x,R.y+y);
}
Point operator -(const Point &R) {
return Point(R.x-x,R.y-y);
}
ld operator *(const Point &R) {
return R.x*x+R.y*y;
}
Point operator *(const ld &R) {
return Point(x*R,y*R);
}
void print() {
double o1=x,o2=y;
cout<<o1<<" "<<o2<<"\n";
}
};
#define sqr(x) ((x)*(x))
ld inv_circle(Point O,Point C,ld r)
{
return IR2*r/(sqr(O-C)-sqr(r));
}
int main()
{
int T;
scanf("%d",&T);
Point O(0,0);
while (T--) {
double t1,t2;
scanf("%lf%lf",&t1,&t2);
if (t1>t2) swap(t1,t2);
ld r=t1,R=t2;
int n;
scanf("%d",&n);
Point P(0.5*IR2/R,0);
Point Q(0.5*IR2/r,0);
ld L=Q.x-P.x;
Point o((P+Q)*0.5);
ld ans=0;
if (n%2==0) {
Point C(o.x,o.y+(n/2)*L);
ld rr=inv_circle(O,C,L*0.5);
ans+=PI*rr*rr;
}
for (int i=1;i+i-1<=n;i++) {
Point C(o.x,o.y+(i-1)*L);
ld rr=inv_circle(O,C,L*0.5);
ld area=PI*rr*rr;
if (area<1e-12) break;
ans+=area;
if (i>1) ans+=area;
}
double out=ans;
printf("%.5f\n",out);
}
return 0;
}
|
