Go: package main

import (
	"fmt"
	"math"
)

func main() {
	var num int
	fmt.Scan(&num)
	for i := 0; i < num; i++ {
		var x1, y1, x2, y2, x3, y3 float64
		fmt.Scanf("%f%f%f%f%f%f", &x1, &y1, &x2, &y2, &x3, &y3)

		a := 2 * (x2 - x1)
		b := 2 * (y2 - y1)
		c := 2 * (x3 - x1)
		d := 2 * (y3 - y1)
		e := x2*x2 - x1*x1 + y2*y2 - y1*y1
		f := x3*x3 - x1*x1 + y3*y3 - y1*y1

		// 直線1: ax + by - e = 0
		// 直線2: cx + dy - f = 0
		px := (d*e - b*f) / (a*d - b*c)
		py := (c*e - a*f) / (b*c - a*d)
		r := math.Sqrt((px-x1)*(px-x1) + (py-y1)*(py-y1))
		fmt.Printf("%.3f %.3f %.3f\n", px, py, r)
	}
}

C++: //#define _GRIBCXX_DEBUG
#include <algorithm>
#include <cctype>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <list>
#include <map>
#include <memory>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;


// ?????¬???????????¬??????
#pragma region MACRO
#define P(x) cout << (x) << endl
#define p(x) cout << (x)
#define PED cout << "\n"
#define rep(i,n) for(int i=0; i<(int)n; ++i)
#define REP(i,x,n) for(int i=x; i<(int)n; ++i)
#define repi(i,n) for(int i=0; i<=(int)n; ++i)
#define REPI(i,x,n) for(int i=x; i<=(int)n; ++i)
#define ILP while(true)
#define FOR(i,c) for(__typeof((c).begin())!=(c).begin(); i!=(c).end(); ++i)
#define ALL(c) (c).begin(), (c).end()
#define mp make_pair
#pragma endregion

#pragma region TYPE_DEF
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<string, string> pss;
typedef pair<string, int> psi;
typedef pair<int, string> pis;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector<long> vl;
typedef vector<long long> vll;
typedef vector<string> vs;
#pragma endregion


// Effective std
#pragma region ESTD
template<typename C, typename T>
constexpr int count(C& c, T t) { return count(ALL(c), t); }
template<typename C, typename F>
constexpr int count_if(C& c, F f) { return count_if(ALL(c), f); }
template<typename C, typename T, typename U>
constexpr void replace(C& c, T t, U u) { replace(ALL(c), t, u); }
template<typename C, typename F, typename U>
constexpr void replace_if(C& c, F f, U u) { (ALL(c), f, u); }
template<typename C>
constexpr void sort(C& c) { sort(ALL(c)); }
template<typename C, typename Pred>
constexpr void sort(C& c, Pred p) { sort(ALL(c), p); }
template<typename C>
constexpr void reverse(C& c) { reverse(ALL(c)); }
#pragma endregion


// ?´???°
#pragma region PRIME
bool is_prime(unsigned n) {
  switch(n) {
    case 0:
    case 1: return false;
    case 2: return true;
  }
  if (n%2==0) return false;
  for (unsigned i=3; i*i<=n; i+=2)
    if (n%i==0) return false;
  return true;
}
#pragma endregion


// ??§??????/?°?????????????
#pragma region TRANSFORM
void mutal_tr(string &s) {
  for(int i=s.size(); i--;) {
    if(islower(s[i])) s[i] = toupper(s[i]);
    else if (isupper(s[i])) s[i] = tolower(s[i]);
  }
}
void to_upper(string &s) { for(int i=s.size(); i--;) s[i] = toupper(s[i]); }
void to_lower(string &s) { for(int i=s.size(); i--;) s[i] = tolower(s[i]); }
#pragma endregion


// ??????
#pragma region SET
template<class T>
set<T> intersection(const set<T>& sa, const set<T>& sb) {
  set<T> ret;
  for(T a : sa) if(sb.find(a) != sb.end()) ret.insert(a);
  return ret;
}
#pragma endregion

// Union Find
#pragma region UF
struct UnionFind {
  vector<int> data;
  UnionFind(int size) : data(size, -1) {}
  bool union_set(int x, int y) {
    x = root(x); y = root(y);
    if(x!=y) {
      if(data[y] < data[x]) swap(x, y);
      data[x] += data[y]; data[y] = x;
    }
    return x != y;
  }
  bool find_set(int x, int y) { return root(x) == root(y); }
  int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
  int size(int x) { return -data[root(x)]; }
};
#pragma endregion


// ?????°
#pragma region CONST_VAL
#define PI (2*acos(0.0))
#define EPS (1e-9)
#define MOD (int)(1e9+7)
#pragma endregion

int main()
{
    int n;
    rep(i,n) {
        double x1,y1,x2,y2,x3,y3;
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
        double a = 2 * (x2 - x1);
        double b = 2 * (y2 - y1);
        double c = x1 * x1 - x2 * x2 + y1 * y1 - y2 * y2;
        double d = 2 * (x3 - x2);
        double e = 2 * (y3 - y2);
        double f = x2 * x2 - x3 * x3 + y2 * y2 - y3 * y3;
        double cx = (b * f - c * e)/(a * e - d * b);
        double cy = (a * f - c * d)/(b * d - a * e);
        double r = sqrt((x1 - cx)*(x1 - cx) + (y1 - cy)*(y1 - cy));
        cout << fixed << setprecision(3) << cx << " " << cy << " " << r << endl;
    }
    return 0;
}

C++: #include<complex>
#include<cstdio>
#include<cmath>
using namespace std;
typedef complex<double> P;
#define F(a,b,c) acos((b*b+c*c-a*a)/2/b/c)
int main(){
	int n;
	double d,e,f,g,h,i;
	for(scanf("%d",&n);n--;){
		scanf("%lf%lf%lf%lf%lf%lf",&d,&g,&e,&h,&f,&i);
		P a(d,g),b(e,h),c(f,i);
		double A=abs(b-c),B=abs(c-a),C=abs(a-b),
		s=sin(2*F(A,B,C)),t=sin(2*F(B,C,A)),u=sin(2*F(C,A,B)),v=s+t+u;
		printf("%.3f %.3f %.3f\n",(d*s+e*t+f*u)/v,(g*s+h*t+i*u)/v,A/sin(F(A,B,C))/2);
	}
}

C++: #include <cstdio>
#include <algorithm>
#include <complex>
using namespace std;

#define FOR(i,a,b)  for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)    for (int i=0;i<(n);i++)
#define RREP(i,n)   for (int i=(n)-1;i>=0;i--)
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

typedef long long ll;
typedef complex<double> C;


double dot(C a, C b) {
    return real(conj(a) * b);
}

double cross(C a, C b) {
    return imag(conj(a) * b);
}

C triangle_circumcenter(C a, C b, C c) {
    a -= c;
    b -= c;
    C z = (abs(a) * abs(a) * b - abs(b) * abs(b) * a) / (conj(a) * b - a * conj(b));
    z += c;
    return z;
}

int main() {
    int n;
    scanf("%d", &n);
    while (n--) {
        double x1, y1, x2, y2, x3, y3;
        scanf("%lf%lf%lf%lf%lf%lf", &x1, &y1, &x2, &y2, &x3, &y3);
        C a = C(x1, y1);
        C b = C(x2, y2);
        C c = C(x3, y3);
        C z = triangle_circumcenter(a, b, c);
        printf("%.3f %.3f %.3f\n", real(z), imag(z), abs(z-c));
    }
    return 0;
}