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 <set>
#include <map>
#include <list>
#include <queue>
#include <stack>
#include <cmath>
#include <ctype.h>
#include <ctime>
#include <cstdio>
#include <vector>
#include <string>
#include <bitset>
#include <cctype>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <numeric>
#include <complex>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <iostream>
#include <iterator>
#include <algorithm>

using namespace std;

#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i, n) REP(i, 0, n)
#define lengthof(x) (sizeof(x) / sizeof(*(x)))
#define FILL(ptr, value) FILL_((ptr), sizeof(ptr)/sizeof(value), (value))
template <typename T>
void FILL_(void * ptr, size_t size, T value){
  std::fill((T*)ptr, (T*)ptr+size, value);
}
//4方向ベクトル→↑←↓
int dx[] ={1,0,-1,0};
int dy[] ={0,-1,0,1};

int main()
{
  int N;
  cin >>N;
  double x1,y1,x2,y2,x3,y3;
  for(int i = 0;i < N;i++){
    cin >>x1>>y1>>x2>>y2>>x3>>y3;
    double a =(x1-x2);
    double b =(y1-y2);
    double c = -(pow(x1,2)+pow(y1,2))+(pow(x2,2)+pow(y2,2));
    double d =(x2-x3);
    double e =(y2-y3);
    double f =-(pow(x2,2)+pow(y2,2))+(pow(x3,2)+pow(y3,2));
    double l =(c*e-f*b)/(a*e-d*b);
    double m =(c*d-a*f)/(b*d-a*e);
    double n =-(pow(x1,2)+pow(y1,2))-(l*x1+m*y1);
    double x = -l/2;
    x +=0.0005;
    x =x*1000;
    x =(int)x;
    x =x/1000;
    double y =-m/2;
    y +=0.0005;
    y =y*1000;
    y =(int)y;
    y =y/1000;
    double r =sqrt(pow(l,2)+pow(m,2)-4*n)/2;
    r +=0.0005;
    r =r*1000;
    r =(int)r;
    r =r/1000;
    printf("%.3f %.3f %.3f\n",x,y,r);
  }
  
  return 0;
}

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

void crpt(double a1, double b1, double c1, double a2, double b2, 
	double c2, double *x, double *y) {

	*x = (b2 * c1 - b1 * c2) / (a1 * b2 - a2 * b1);
	*y = (a1 * c2 - a2 * c1) / (a1 * b2 - a2 * b1);
}

int main()
{
	int n;
	double x1, y1, x2, y2, x3, y3;

	cin >> n;

	for (int i = 0; i < n; i++) {
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

		double px, py, r;

		crpt(x2 - x1, y2 - y1, (x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1) / 2, 
			x3 - x1, y3 - y1, (x3 * x3 - x1 * x1 + y3 * y3 - y1 * y1) / 2, &px, &py);

		r = sqrt((px - x1) * (px - x1) + (py - y1) * (py - y1));

		cout << setiosflags(ios::fixed | ios::showpoint) << setprecision(3)
			<< px << " " << py << " " << r << endl;
	}

	return 0;
}

C++: #include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
int main() {
  int n;
  cin>>n;
  double a,b,c,d,e,f,x,y,r,x1,x2,x3,y1,y2,y3;
  for(int i=0;i<n;i++) {
    cin>>x1>>y1>>x2>>y2>>x3>>y3;
    a = sqrt((x3 - x2) * (x3 - x2) + (y3 - y2) * (y3 - y2));
    b = sqrt((x1 - x3) * (x1 - x3) + (y1 - y3) * (y1 - y3));
    c = sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
    d = acos((b * b + c * c - a * a) / (2 * b * c));
    e = acos((a * a + c * c - b * b) / (2 * a * c));
    f = acos((b * b + a * a - c * c) / (2 * b * a));
    x = (x1 * sin(d * 2) + x2 * sin(e * 2) + x3 * sin(f * 2)) / (sin(d * 2) + sin(e * 2) + sin(f * 2));
    y = (y1 * sin(d * 2) + y2 * sin(e * 2) + y3 * sin(f * 2)) / (sin(d * 2) + sin(e * 2) + sin(f * 2));
    r = a / (2 * sin(d));
    cout<<fixed<<setprecision(3)<<x<<" "<<y<<" "<<r<<endl;
  }
  return 0;
}

C++: #include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
 
int main(){
	int n;
	cin >> n;
	for(int i = 0; i < n; i++){
		double x[3], y[3], a1, a2, b1, b2, px, py, r;
		for(int i = 0; i < 3; i++){
			cin >> x[i] >> y[i];
		}
		bool check = true;
		if(y[1]-y[0] == 0){
			px = (x[1]+x[0])/2;
			check = false;
		}else{
			a1 = (x[0]-x[1])/(y[1]-y[0]);
			b1 = (y[1]+y[0])/2-a1*(x[1]+x[0])/2;
		}
		if(y[2]-y[0] == 0){
			px = (x[2]+x[0])/2;
			check = false; 
		}else{
			a2 = (x[0]-x[2])/(y[2]-y[0]);
			b2 = (y[2]+y[0])/2-a2*(x[2]+x[0])/2;
		}
		if(check){
			px = (b2-b1)/(a1-a2);
			py = a1*px+b1;	
		}else if(y[1]-y[0] == 0){
			py = a2*px+b2;
		}else if(y[2]-y[0] == 0){
			py = a1*px+b1;
		}
		r = pow(px-x[0], 2)+pow(py-y[0], 2);
		r = sqrt(r);
		cout << fixed << setprecision(3) << px << ' ' << py << ' ' << r << endl;
	}
}