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;

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  
  int n;
  cin >> n;
  for (int i = 0; i < n; i ++) {
    double a, b, c, d, e, f, px, py, r;
    cin >> a >> b >> c >> d >> e >> f;
    py = ((e - a) * (a*a + b*b - c*c - d*d) - (c - a) * (a*a + b*b - e*e - f*f)) / (2 * (e - a) * (b - d) - 2 * (c - a) * (b - f));
    if (c == a) {
      px = (2 * (b - f) * py - a*a - b*b + e*e + f*f) / (2 * (e - a));
    } else {
      px = (2 * (b - d) * py - a*a - b*b + c*c + d*d) / (2 * (c - a));
    }
    r = sqrt((px - a) * (px - a) + (py - b) * (py - b));
    cout << fixed;
    cout << setprecision(3) << px << " " << setprecision(3) << py << " " << setprecision(3) << r << endl;
  }
}

C++: #include <iostream>
#include <cmath>
#include <cstdio>
#define MAX_N 20
using namespace std;

void swap(double &x,double &y){
	double t;
	t=x;
	x=y;
	y=t;
}

double cut4(double x){
	double temp=x*1000;
	temp=(temp+0.5)/1000;
	return temp;
}

int main(){
	int n;
	double x1,x2,x3,y1,y2,y3,px,py;
	double a,b,c,d,r;
	cin>>n;
	for(int i=0;i<n;i++){
		cin>>x1>>y1>>x2>>y2>>x3>>y3;
		if(x1==x2){
			swap(x2,x3);
			swap(y2,y3);
		}else if(x2==x3){
			swap(x1,x2);
			swap(y1,y2);
		}
		a=(y2-y1)/(x2-x1);
		c=(y3-y2)/(x3-x2);
		if(a&&c){
			a=-1/a;
			c=-1/c;
			b=(y1+y2)/2-a*(x1+x2)/2;
			d=(y2+y3)/2-c*(x2+x3)/2;
			px=(b-d)/(c-a);
			py=(b*c-a*d)/(c-a);
		}else if(!a){
			c=-1/c;
			d=(y2+y3)/2-c*(x2+x3)/2;
			px=(x1+x2)/2;
			py=c*(x1+x2)/2+d;
		}else if(!c){
			a=-1/a;
			b=(y1+y2)/2-a*(x1+x2)/2;
			px=(x2+x3)/2;
			py=a*(x2+x3)/2+b;
		}

		r=sqrt((px-x1)*(px-x1)+(py-y1)*(py-y1));
//		px=(px==0?0.000:px);
//		py=(py==0?0.000:py);
		printf("%.3lf %.3lf %.3lf\n",px,py,r);
	}
	return 0;
}

C++: #include <stdio.h>
#include <math.h>
 
using namespace std;
 
 
int main(){
    int n;
    double x1,x2,x3,y1,y2,y3,ox,oy,r;
    scanf("%d",&n);
 
    for(int i=0;i<n;i++){
        scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3);
        ox=((y2-y1)*((y3*y3-y1*y1)+(x3*x3-x1*x1))-(y3-y1)*((y2*y2-y1*y1)+(x2*x2-x1*x1)))/
                (2*((x3-x1)*(y2-y1)-(x2-x1)*(y3-y1)));
        if(y2 != y1){
            oy=(2*(x1-x2)*ox+(y2*y2-y1*y1)+(x2*x2-x1*x1))/(2*(y2-y1));
        }else{
            oy=(2*(x1-x3)*ox+(y3*y3-y1*y1)+(x3*x3-x1*x1))/(2*(y3-y1));
        }
 
        r = sqrt((ox-x1)*(ox-x1)+(oy-y1)*(oy-y1));
        printf("%.3lf %.3lf %.3lf\n",ox,oy,r);
    }
    return 0;
}

C++: #include <stdio.h>
#include <math.h>

int main()
{
  int setcount;
  float x1, y1, x2, y2, x3, y3;
  float nx1, ny1, nx2, ny2;
  float nr1, nr2;
  float xp, yp, r;
  int tx, ty, tr, rem;
  int i;

  scanf("%d", &setcount);
  for(i=0; i<setcount; i++){

    xp=nr1+x1; yp=nr2+y1;
    r=(float)sqrt((double)(nr1^2+nr2^2));
    tx=xp*10000; ty=yp*10000; tr=r*10000;
    if((rem=tx%10)<5) tx-=rem;
    else tx+=10-rem;
    if((rem=ty%10)<5) ty-=rem;
    else ty+=10-rem;
    if((rem=tr%10)<5) tr-=rem;
    else tr+=10-rem;
    xp=(float)tx*0.0001f; yp=(float)ty*0.0001f; r=(float)tr*0.0001f;

    printf("%.3f %.3f %.3f\n", xp, yp, r);
  }

  return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <math.h>
using namespace std;
int main(){
	int n;
	cin >> n;
	for(int i=0;i<n;i++){
		double x1,x2,x3,y1,y2,y3;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		double c1 = 2.0*(x1-x2);
		double c2 = 2.0*(y1-y2);
		double c3 = 2.0*(x1-x3);
		double c4 = 2.0*(y1-y3);
		double c5 = x1*x1 + y1*y1;
		double c6 = x2*x2 + y2*y2;
		double c7 = x3*x3 + y3*y3;
		double px = (c4*(c5-c6)-c2*(c5-c7))/(c1*c4-c2*c3);
		double py = (c5-c6-c2*py)/c1;
		double r = sqrt((px-x1)*(px-x1)+(py-y1)*(py-y1));
		cout << fixed << setprecision(3) << px << " " << py << " " << r << endl;
	}
}

C++: #include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int main()
{
	double n;
	double x1, x2, x3;
	double y1, y2, y3;
	cin >> n;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	double px, py, r;
	double A = (x2 - x1)*(y3 - y2) - (y2 - y1)*(x3 - x2);
	px = 0.5*((y3 - y2)*(x2*x2 - x1*x1 + y2*y2 - y1*y1) - (y2 - y1)*(x3*x3 - x2*x2 + y3*y3 - y2*y2)) / A;
	py = 0.5*(-(x3 - x2)*(x2*x2 - x1*x1 + y2*y2 - y1*y1) + (x2 - x1)*(x3*x3 - x2*x2 + y3*y3 - y2*y2)) / A;
	double a = px - x1;
	double b = py - y1;
	double r0 = (a*a + b*b);
	double r1 = sqrt(r0);
	cout << fixed << setprecision(10) << px << ' ' << py << ' ' << r1 <<  endl;
}