Go: package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
	"strings"

)


func main() {
	solve(os.Stdin, os.Stdout)
}

type ReaderEx struct {
	baseScanner *bufio.Scanner
	words       []string
	nextWordIdx func() int
	initWordIdx func(int)
}

func NewScannerEx(stdin io.Reader) *ReaderEx {
	var this ReaderEx
	var idx int
	var wordsCnt int
	this.baseScanner = bufio.NewScanner(stdin)
	this.baseScanner.Buffer(make([]byte, 0), 1E+11)
	this.nextWordIdx = func() int {
		cur := idx
		idx = (idx + 1) % wordsCnt
		return cur
	}
	this.initWordIdx = func(wc int) {
		idx = 0
		wordsCnt = wc
	}
	return &this
}

func (me *ReaderEx) Scan(doSplit bool) (isScanned bool) {
	isScanned = me.baseScanner.Scan()
	if doSplit {
		me.words = strings.Fields(me.baseScanner.Text())
	} else {
		me.words = []string{me.baseScanner.Text()}
	}
	me.initWordIdx(len(me.words))
	return
}

func (me *ReaderEx) nextBytes() []byte {
	return []byte(me.words[me.nextWordIdx()])
}
func (me *ReaderEx) nextString() string {
	return me.words[me.nextWordIdx()]
}

type StringArray []string

func (me *ReaderEx) nextStringArray() StringArray {
	return me.words[me.nextWordIdx():]
}

func (me StringArray) toStrings() []string {
	return me
}

func (me StringArray) toInts() []int {
	strValues := me.toStrings()
	values := make([]int, len(strValues))
	for i, v := range strValues {
		n, err := strconv.Atoi(v)
		if err != nil {
			panic(err)
		}
		values[i] = n
	}
	return values
}
func (me *ReaderEx) nextInt() int {
	n, err := strconv.Atoi(me.words[me.nextWordIdx()])

	defer func() {
		if err != nil {
			panic(fmt.Sprintf("getInt(%d)", n))
		}
	}()
	return n
}

func pow(x, y, mod int) (ans int) {

	ans = 1
	for bit := 1 << uint(math.Floor(math.Log2(float64(y)))); ; bit >>= 1 {
		if y&bit != 0 {
			ans *= x
			if mod > 0 {
				ans %= mod
			}
		}
		if bit <= 1 {
			return
		}
		ans *= ans
		if mod > 0 {
			ans %= mod
		}
	}
}

type factType struct {
	prime int
	count int
}

func fact(n int) (facts []*factType) {

	for i := 2; i*i <= n; i++ {
		if n%i == 0 {
			fa := factType{prime: i}
			for n%fa.prime == 0 {
				n /= fa.prime
				fa.count++
			}
			facts = append(facts, &fa)
		}
	}
	if n > 1 {
		facts = append(facts, &factType{prime: n, count: 1})
	}
	return facts
}
func dec2bin(n int) (ret []bool) {
	for bit := 1 << uint(math.Floor(math.Log2(float64(n)))); ; bit >>= 1 {
		ret = append(ret, n&bit != 0)

		if bit <= 1 {
			return
		}
	}

}

func abs(v int) int {
	if v < 0 {
		v = -v
	}
	return v
}

func b2i(b bool) (i int) {
	if b {
		i = 1
	} else {
		i = 0
	}
	return
}

func solve(stdin io.Reader, stdout io.Writer) {

	r := NewScannerEx(stdin)
	r.Scan(true)
	n := r.nextInt()

	type Vec struct {
		x, y float64
	}
	vec := func(a, b Vec) Vec { return Vec{b.x - a.x, b.y - a.y} }
	unv := func(a Vec) Vec { return Vec{-a.y, a.x} }
	cdot := func(a, b Vec) float64 { return a.x*b.x + a.y*b.y }
	times := func(t float64, a Vec) Vec { return Vec{t * a.x, t * a.y} }
	add := func(a, b Vec) Vec { return Vec{a.x + b.x, a.y + b.y} }
	for i := 0; i < n; i++ {

		r.Scan(true)
		nextFloat64 := func() (ret float64) { fmt.Sscanf(r.nextString(), "%f", &ret); return }
		a1, a2, a3 := Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}
		unv23 := unv(vec(a2, a3))
		v12 := vec(a1, a2)
		v31 := vec(a3, a1)
		s := cdot(v12, v31) / 2 / cdot(v12, unv23)
		c := add(times(.5, add(a2, a3)), times(s, unv23))
		v1c := vec(a1, c)
		fmt.Fprintf(stdout, "%.3f %.3f %.3f\n", c.x, c.y, math.Sqrt(v1c.x*v1c.x+v1c.y*v1c.y))
	}
}

C++: #include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <memory.h>
#include <cmath>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <ctime>
#include <iostream>
#include <functional>
#include <complex>
#include <iomanip>
#pragma comment(linker, "/STACK:836777216")

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef pair<pii, int> p3i;
typedef vector<int> vi;
typedef vector<pii> vii;
typedef vector<pll> vll;
typedef vector<p3i> v3i;
typedef vector<vii> vvii;
typedef vector<p3i> vp3i;
typedef long double ld;
typedef vector<ld> vld;

#define pb push_back
#define mp make_pair
#define REP(i, n) for (int (i) = 0; (i) < (n); (i)++)
#define REPD(i, n) for (int (i) = (n) - 1; (i) >= 0; (i)--)
#define FOR(i, a, b) for (int (i) = (a); (i) < (b); (i)++)
#define FORD(i,a, b) for (int (i) = (a); (i) >= (b); (i)--)
#define sz(v) (int)(v).size()
#define all(v) (v).begin(), (v).end()
#define rv(v) reverse(all(v))
#define CL(v, val) memset((v), (val), sizeof((v)))
#define SORT(a) sort(all(a))
#define un(v) SORT(v), (v).resize(unique(all(v)) - (v).begin())
#define eps 1.0e-7
#define X first
#define Y second
#define bit(n) (1 << (n))
#define bit64(n) (ll(1) << (n))
#define sqr(n) ((n) * (n))

double x[3], y[3];
double l[3];

double GetDist(int a, int b) {
  return sqrt(sqr(x[a] - x[b]) + sqr(y[a] - y[b]));
}

int main(void) {
  int n;
  scanf("%d", &n);
  REP(i, n) {
    REP(j, 3) {
      scanf("%lf%lf", &x[j], &y[j]);
    }

    double D = 2 * (x[0] * (y[1] - y[2]) + x[1] * (y[2] - y[0]) + x[2] * (y[0] - y[1]));
    double xc = 1.0 / D * ((sqr(x[0]) + sqr(y[0])) * (y[1] - y[2]) + (sqr(x[1]) + sqr(y[1])) * (y[2] - y[0]) + (sqr(x[2]) + sqr(y[2])) * (y[0] - y[1]));
    double yc = 1.0 / D * ((sqr(x[0]) + sqr(y[0])) * (x[2] - x[1]) + (sqr(x[1]) + sqr(y[1])) * (x[0] - x[2]) + (sqr(x[2]) + sqr(y[2])) * (x[1] - x[0]));

    double p = 0;
    REP(j, 3) {
      l[j] = GetDist(j, (j + 1) % 3);
      p += l[j];
    }

    p /= 2;

    double r = 1;
    double z = p;
    REP(j, 3) {
      r *= l[j];
      z *= (p - l[j]);
    }

    r = r / (4 * sqrt(z));

    printf("%.3lf %.3lf %.3lf\n", xc, yc, r);


  }
  return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>
#include <utility>
using namespace std;


class vec{
public:
	double x;
	double y;
	double normEXP2() const{
		return x*x + y*y;
	}
	vec& operator+(const vec& v){
		x += v.x;
		y += v.y;
		return *this;
	}
	vec& operator-(const vec& v){
		x -= v.x;
		y -= v.y;
		return *this;
	}
	vec& operator*(double scala){
		x *= scala;
		y *= scala;
		return *this;
	}
	double operator*(const vec& v) const{
		return x*v.x + y*v.y;
	}
};


istream& operator>>(istream& i, vec& v){
	i >> v.x >> v.y;
	return i;
}


pair<double, double> cramer(const vec& a, const vec& b){
	pair<double, double> solve;
	solve.first = (2 * a.normEXP2()*b.normEXP2() - 2 * b.normEXP2()*(a*b)) / (4 * a.normEXP2()*b.normEXP2() - 4 * ((a*b)*(a*b)));
	solve.second = (2 * a.normEXP2()*b.normEXP2() - 2 * a.normEXP2()*(a*b)) / (4 * a.normEXP2()*b.normEXP2() - 4 * ((a*b)*(a*b)));

	return solve;
}


int main(){
	int n;
	vec v1, v2, v3;
	vec b, c;
	vec solveVec;
	pair<double, double> solve;
	double x, y;
	double r;

	cin >> n;
	for (int i = 0; i < n; i++){
		cin >> v1 >> v2 >> v3;
		b = v2 - v1;
		c = v3 - v1;
		
		solve = cramer(b, c);
		solveVec = (b*solve.first) + (c*solve.second);

		solveVec = v1 + solveVec;
		r = sqrt(solveVec.normEXP2());

		y = (double)((int)((solveVec.y * 1000) + 0.5)) / 1000;
		r = (double)((int)((r * 1000) + 0.5)) / 1000;
		x = (double)((int)((solveVec.x * 1000) + 0.5)) / 1000;

		printf("%.3lf %.3lf %.3lf\n", x, y, r);
	}

	return 0;
}

C++: int main(void){

  int n;
  cin >> n;

  for(int i = 0;i < n;i++){

    double x1,y1,x2,y2,x3,y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

    double a = sqrt(pow(x2-x1,2) + pow(y2-y1,2));
    double b = sqrt(pow(x3-x2,2) + pow(y3-y2,2));
    double c = sqrt(pow(x3-x1,2) + pow(y3-y1,2));

    double r = a*b*c / sqrt((a+b+c)*(-a+b+c)*(a-b+c)*(a+b-c));

    double A = pow(x2-x1,2) + pow(y2-y1,2);
    double B = pow(x3-x2,2) + pow(y3-y2,2);
    double C = pow(x3-x1,2) + pow(y3-y1,2);
    double s = 4*((x2-x1)*(y3-y1) -(x3-x1)*(y2-y1));

    double x = A*(B+C-A) / s;
    double y = B*(C+A-B) / s;

    printf("%.3f %.3f %.3f\n");

  }




  return 0;
}