對每個圓作切線，求出投影區(qū)間，最后全部求并
/**//*************************************************************************
Author: WHU_GCC
Created Time: 2007-8-12 15:52:30
File Name: pku1375.cpp
Description:
************************************************************************/
#include <algorithm>
#include <iostream>
#include <cmath>
using namespace std;
#define out(x) (cout<<#x<<": "<<x<<endl)
const int maxint=0x7FFFFFFF;
typedef long long int64;
const int64 maxint64 = 0x7FFFFFFFFFFFFFFFLL;
template<class T>void show(T a, int n)
{for(int i=0; i<n; ++i) cout<<a[i]<<' '; cout<<endl;}
template<class T>void show(T a, int r, int l){for(int i=0; i<r; ++i)show(a[i],l);cout<<endl;}
const double eps = 1e-9;
typedef struct point_t
{
int x, y;
};
typedef struct interval_t
{
double l, r;
};
bool operator <(const interval_t &a, const interval_t &b)
{
return a.l < b.l || a.l == b.l && a.r < b.r;
}
double dist(point_t b, point_t c)
{
return sqrt((b.x - c.x) * (b.x - c.x) + (b.y - c.y) * (b.y - c.y));
}
interval_t get_inter(point_t b, point_t c, int r)
{
double alpha, beta, d = dist(b, c);
beta = asin((c.x - b.x) / d);
alpha = asin(r / d);
double p1 = tan(beta - alpha) * b.y + b.x;
double p2 = tan(beta + alpha) * b.y + b.x;
interval_t ret;
ret.l = p1;
ret.r = p2;
return ret;
}
point_t c[600];
int r[600];
point_t b;
int n;
interval_t inter[600];
int main()
{
while (scanf("%d", &n), n != 0)
{
scanf("%d%d", &b.x, &b.y);
for (int i = 0; i < n; i++)
scanf("%d%d%d", &c[i].x, &c[i].y, &r[i]);
for (int i = 0; i < n; i++)
inter[i] = get_inter(b, c[i], r[i]);
sort(inter, inter + n);
double l = inter[0].l, r = inter[0].r;
for (int i = 1; i < n; i++)
{
if (inter[i].l < r + eps)
r >?= inter[i].r;
else
{
printf("%.2lf %.2lf\n", l, r);
l = inter[i].l;
r = inter[i].r;
}
}
printf("%.2lf %.2lf\n", l, r);
printf("\n");
}
return 0;
}