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<iostream>
#include<cmath>
#include<algorithm>
#define SQ(x) ((x)*(x))
using namespace std;

int main(){
  int n;
  double x1,y1,x2,y2,x3,y3;
  double a,b,c,d,e,f,l,C,r,xp,yp,m; // 3辺
  cin >> n;
    for(int i=0;i<n;i++){
      cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
      a = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
      b = sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
      c = sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
      C = fabs(1.0-C*C);
      if(C == 0)C = 1;
      if(c == 0)c = 1;
      C = (sqrt(C)); // sinθに変更
      r = (c/2*C); // 接弦定理
    
      a = (x1 - x2);
      b = (y1 - y2);
      c = -1 * (SQ(x1) - SQ(x2) + SQ(y1) - SQ(y2));
      d = (x1 - x3);
      e = (y1 - y3);
      f = -1 * (SQ(x1) - SQ(x3) + SQ(y1) - SQ(y3));
    
      l = (c * e - b * f) / (e * a - b * d);
      m = (d * c - a * f) / (d * b - e * a);
    
      printf("%.3f %.3f %.3f\n", l / -2.0, m / -2.0, r);
  }
}

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

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

    cin >> num;

    for( int i = 0; i < num; i++ )
    {
        double px = 0, py = 0, r = 0;
        cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;

        py = (-x2*x3*x3+x2*x2*x3-x2*y3*y3+y2*y2*x3) / (2*x3*y2-2*x2*y3);
        px = (2*(y1-y2)*py+x2*x2-x1*x1+y2*y2-y1*y1) / (2*x2-2*x1);
        r = (px-x1)*(px-x1) + (py-y1)*(py-y1);

        cout << fixed;
        cout << setprecision(3) << px << " " << py << " " << sqrt(r) << endl;

    }



    return 0;
}

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

#define t(a) (a)*(a)

using namespace std;

int main(){
    double x[3],y[3],a1,a2,b1,b2,c1,c2,rx,ry,r;
    int n;
    cin >> n;
    for(int j=0;j<n;j++){
        for(int i=0;i<3;i++) cin >> x[i] >> y[i];
        a1 = 2*(x[1]-x[0]);
        b1 = 2*(y[1]-y[0]);
        c1 = t(x[0])-t(x[1])+t(y[0])-t(y[1]);
        a2 = 2*(x[2]-x[0]);
        b2 = 2*(y[2]-y[0]);
        c2 = t(x[0])-t(x[2])+t(y[0])-t(y[2]);
        rx = (b1*c2-b2*c1)/(a1*b2-a2*b1);
        ry = (c1*a2-c2*a1)/(a1*b2-a2*b1);
        r=sqrt(t(x[0]-rx)+t(y[0]-ry));
        printf("%.3f %.3f %.3f\n",rx,ry,r);
    }
    return 0;
}

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

using namespace std;

int main(){
	int n;
	cin >> n;

	for(int i=0; i<n; i++){
		double x1, y1, x2, y2, x3, y3;
		double px, py, r;

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

		px = (x1 + x2 + x3) / 3;
		py = (y1 + y2 + y3) / 3;
		r = sqrt((x1-px)*(x1-px) + (y1-py)*(y1-py));

		printf("%.3f %.3f %.3f\n", px, py, r);
	}

	return 0;
}

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

using namespace std;

const double eps = 1e-12;

int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        complex<double> p1, p2, p3, m1, m2, d1, d2;
        cin >> p1.real() >> p1.imag() >> p2.real() >> p2.imag() >> p3.real() >> p3.imag();
        m1 = (p1 + p2) / 2.0;
        m2 = (p2 + p3) / 2.0;
        d1 = polar(1.0, arg(p2 - p1) + M_PI_2);
        d2 = polar(1.0, arg(p3 - p2) + M_PI_2);
        
        double t;
        t = (d1.real() * m1.imag() + d1.imag() * m2.real() - m1.real() * d1.imag() - d1.real() * m2.imag()) / (d1.real() * d2.imag() - d2.real() * d1.imag());
        
        double x = m2.real() + t * d2.real();
        double y = m2.imag() + t * d2.imag();
        double r = abs(complex<double>(x,y) - p1);
        
        printf("%.3lf %.3lf %.3lf\n", x, y, r);
    }
    return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>

using namespace std;

int main() {
  int n;
  double x1, x2, x3, y1, y2, y3;
  double a1, a2, b1, b2, c1, c2;
  double x, y, r;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    a1 = 2*(x2 - x1);
    b1 = 2*(y2 - y1);
    c1 = x1*x1 - x2*x2 + y1*y1 - y2*y2;

    a2 = 2*(x3 - x1);
    b2 = 2*(y3 - y1);
    c2 = x1*x1 - x3*x3 + y1*y1 - y3*y3;

    x = (b1*c2 - b2 * c1) / (a1*b2 - a2*b1);
    y = (c1*a2 - c2*a1) / (a1*b2 - a2*b1);
    r = sqrt((x-x1)*(x-x1) + (y-y1)*(y-y1));

    x += 0.0005;
    y += 0.0005;
    r += 0.0005;

    x *= 1000;
    y *= 1000;
    r *= 1000;

    cout << fixed << setprecision(3) << ((double)((int)x))/1000 << " " << ((double)((int)y))/1000 << " " << ((double)((int)r))/1000 << endl;
  }
  return 0;
}