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 <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int INF = 1000000000;
#define REP(i,s,n) for(int i=(int)(s);i<(int)(n);i++)
#define rep(i,n) REP(i, 0, n)
typedef complex<double> Point;
const double EPS = 1.0e-9;
const double PI = acos(-1);
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int test; cin >> test;
    rep(casenum, test){
        Point a, b, c, m1, m2, d1, d2;
        cin >> a.real() >> a.imag() >> b.real() >> b.imag() >> c.real() >> c.imag();
        m1 = (a + b) / 2.0, m2 = (b + c) / 2.0;//????????¨???????????????, ????????¨????????????
        double s1 = arg(b - a) + PI / 2.0, s2 = arg(c - b) + PI / 2.0;//?????¨??´???????????????
        d1 = polar(1.0, s1), d2 = polar(1.0, s2);
        Point mn = m2 - m1;
        double q = (mn.real() / d1.real() - mn.imag() / d1.imag()) / (d2.real() / d1.real() - d2.imag() / d1.imag());
        q *= -1;
        double x = m2.real() + q * d2.real();
        double y = m2.imag() + q * d2.imag();
        double r = abs(Point(x, y) - a);
        cout << x << ' ' << y << ' ' << r << endl;

        printf("%.3lf %.3lf %.3lf\n", x, y, r);
    }
    return 0;
}

C++: /* {{{ Shinobu kawaii */
/*
  ______   __        _                  __                 
.' ____ \ [  |      (_)                [  |                
| (___ \_| | |--.   __   _ .--.   .--.  | |.--.   __   _   
 _.____`.  | .-. | [  | [ `.-. |/ .'`\ \| '/'`\ \[  | | |  
| \____) | | | | |  | |  | | | || \__. ||  \__/ | | \_/ |, 
 \______.'[___]|__][___][___||__]'.__.'[__;.__.'  '.__.'_/ 
                                                           
*/
/* }}} */
/* include {{{ */
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <iostream>
#include <vector>
#include <string>
#include <sstream>
#include <algorithm>
#include <utility>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <functional>
using namespace std;
/* }}} */

// #define int long long

/* cpp template {{{ */
/* short */
#define pb push_back
#define mp make_pair
#define print(x) cout << x << '\n'
#define Fi first
#define Se second

/* REPmacro */
#define REPS(i, a, n) for (int i = (a); i < (n); i++)
#define REP(i, n) for (int i = 0; i < (n); i++)
#define RREP(i, n) for (int i = 1; i <= (n); i++)
#define DEPS(i, a, n) for (int i = (a); i >= n; i--)
#define DEP(i, n) for (int i = (n); i >= 0; i--)

/* typedef */
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef vector<vector<int> > vii;
typedef pair<int, int> pii;

/* const */
const int INF = 999999999;
const double EPS = 1e-12;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool is_uruu(int y) {return (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0));}
inline bool inside(int y, int x, int H, int W) {return (y >= 0 && x >= 0 && y < H && x < W);}

/* }}} */

#define sq(x) ((x) * (x))

signed main()
{
  cin.tie(0);
  ios::sync_with_stdio(false);

  int n;
  cin >> n;

  while (n--){
    double x1, y1, x2, y2, x3, y3;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

    double a = 2 * (x1 - x2), b = 2 * (y1 - y2),
           c = 2 * (x1 - x3), d = 2 * (y1 - y3);

    double y = (c * (sq(x1) * sq(y1) - sq(x2) - sq(y2)) - a * (sq(x1) + sq(y1) - sq(x3) - sq(y3))) / (c * b == a * d ? EPS : c * b - a * d);
    double x = (sq(x1) + sq(y1) - sq(x3) - sq(y3) - d * y) / (c == 0 ? EPS : c);
    double r = sqrt(sq(x - x1) + sq(y - y1));
    printf("%.3f %.3f %.3f\n", x, y, r);
  }

  return (0);
}

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

int main(void)
{
    int n;
    double x1, x2, x3, y1, y2, y3;
    cin >> n;
    while (cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3) {
        double a = 2 * (x1 - x2);
        double b = 2 * (y1 - y2);
        double c = x1*x1 - x2*x2 + y1*y1 - y2*y2;
        double d = 2 * (x1 - x3);
        double e = 2 * (y1 - y3);
        double f = x1*x1 - x3*x3 + y1*y1 - y3*y3;
        double p1 = (e * c - b * f) / (e * a - b * d);
        double p2 = (d * c - a * f) / (d * b - a * e);
        double r = sqrt(pow(x1 - p1, 2) + pow(y1 - p2, 2));

        cout << p1 << " " << p2 << " " << r;
    }


    return 0;
}