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++: //#define _USE_MATH_DEFINES
//#include <cmath>
#include <iostream>
#include <stdio.h>
//#include <stdlib.h>
//#include <iomanip>
//#include <vector>
//#include <string>
//#include <algorithm>
//#include <functional>
//#include <time.h>
//#include <sstream>
//#include <queue>

using namespace std;


int main(){

	int n;
	double ax, ay, bx, by, cx, cy;
	double A, B, C,S2;
	double x, y,r;

	cin >> n;

	while (n--){
		cin >> ax >> ay >> bx >> by >> cx >> cy;

		A = (bx - cx)*(bx - cx) + (by - cy)*(by - cy);
		B = (cx - ax)*(cx - ax) + (cy - ay)*(cy - ay);
		C = (bx - ax)*(bx - ax) + (by - ay)*(by - ay);
		S2 = A*(B + C - A) + B*(C + A - B) + C*(A + B - C);

		x = (A*(B + C - A)*ax + B*(C + A - B)*bx + C*(A + B - C)*cx) / S2;
		y = (A*(B + C - A)*ay + B*(C + A - B)*by + C*(A + B - C)*cy) / S2;

		r = sqrt((x - ax)*(x - ax) + (y - ay)*(y - ay));

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

C++: #include <iostream>
#include <cmath>
#include <iomanip>
#define sqr(n) ((n) * (n))
using namespace std;

void equation(double a, double b, double c, double d, double e, double f, double *x, double *y)
{
  *x = (c * e - b * f) / (a * e - b * d);
  *y = (a * f - c * d) / (a * e - b * d);   
}

int main()
{
  int n;
  double x1, y1, x2, y2, x3, y3, x, y;
  cin >> n;
  for(int i = 0; i < n; i++){
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    x = y = 0;
    equation((2.0 * (x2 - x1)), (2.0 * (y2 - y1)), (sqr(x2) + sqr(y2) - sqr(x1) - sqr(y1)), (2.0 * (x3 - x2)), (2.0 * (y3 - y2)), (sqr(x3) + sqr(y3) - sqr(x2) - sqr(y2)), &x, &y);
    cout << fixed << setprecision(3) << x + 0.0001 << ' ' <<  y + 0.0001 << ' ' << sqrt(sqr(x1 - x) + sqr(y1 - y)) + 0.0001 << endl;
  }
}

C++: #include <iostream>
#include <cstdio>
#include <cmath>

using namespace std;

int main() {
    int n;
    double a, b, c, d, e, f;
    double x1, x2, x3, y1, y2, y3, px, py, r;
    cin >> n;
    while (n--) {
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
        a = 2 * (x1 - x2);
        b = 2 * (y1 - y2);
        c = x1*x1 + y1*y1 - x2*x2 - y2*y2;
        d = 2 * (x1 - x3);
        e = 2 * (y1 - y3);
        f = x1*x1 + y1*y1 - x3*x3 - y3*y3;
        px = (c*e - b*f) / (a*e - b*d);
        py = (c*d - a*f) / (b*d - a*e);
        r = sqrt((px - x1)*(px - x1) + (py - y1)*(py - y1));
        printf("%.3f %.3f %.3f\n", px, py, r);
    }
    
    return 0;
}

C++: #include<iostream>
#include<cmath>
#include<stdio.h>
using namespace std;
int main() {
  int n=0,p,q,r;
  double ax=0,ay=0,bx=0,by=0,cx=0,cy=0,S=0,R=0,a=0,b=0,c=0,x=0,y=0;
  cin>>n;
  for(int i=0; i<n; i++){
    cin>>ax>>ay>>bx>>by>>cx>>cy;
    S=abs(((bx-ax)*(cy-ay)-(cx-ax)*(by-ay))/2);
    a=sqrt((cx-bx)*(cx-bx)+(cy-by)*(cy-by));
    b=sqrt((cx-ax)*(cx-ax)+(cy-ay)*(cy-ay));
    c=sqrt((ax-bx)*(ax-bx)+(ay-by)*(ay-by));
    R=a*b*c/(4*S);
    x=(a*a*(b*b+c*c-a*a)*ax+b*b*(c*c+a*a-b*b)*bx+c*c*(a*a+b*b-c*c)*cx)/(16*S*S);
    y=(a*a*(b*b+c*c-a*a)*ay+b*b*(c*c+a*a-b*b)*by+c*c*(a*a+b*b-c*c)*cy)/(16*S*S);
    printf("%.3f %.3f %.3f\n",x,y,R);
  }
}

C++: #include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
double EPS=1e-10;
double add(double a, double b)
{
	if(abs(a+b)<EPS*(abs(a)+abs(b))) return 0;
	return a+b;
}

int main()
{
	int n ; cin >> n ;
	while(n--)
	{
		double x[3],y[3]; for(int i=0;i<3;i++) cin >> x[i] >> y[i] ;
		double a=x[1]-x[0];
		double b=y[1]-y[0];
		double d=x[2]-x[1];
		double e=y[2]-y[1];
		double c=add(-add(x[1]*x[1],-x[0]*x[0])/2,-add(y[1]*y[1],-y[0]*y[0])/2);
		double f=add(-add(x[2]*x[2],-x[1]*x[1])/2,-add(y[2]*y[2],-y[1]*y[1])/2);
		double X=add(b*f,-c*e)/add(a*e,-b*d);
		double Y=add(c*d,-a*f)/add(a*e,-b*d);
		double r=sqrt( add( (X-x[0])*(X-x[0]),(Y-y[0])*(Y-y[0]) ) );
		cout << fixed << setprecision(3) << X  << ' ' << Y << ' ' << r << '\n';
	}
}