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 <cmath>
#include <utility>
using namespace std;

struct Line {
  double a;
  double b;
  double c;
};

typedef pair<double, double> Pair;

int n;
double xs[3];
double ys[3];

double Dist(Pair p1, Pair p2) {
  double dx = p1.first - p2.first;
  double dy = p1.second - p2.second;
  return sqrt(dx*dx+dy*dy);
}

Pair Intersect(Line &l1, Line &l2) {
  double a1 = l1.a;
  double b1 = l1.b;
  double c1 = l1.c;
  double a2 = l2.a;
  double b2 = l2.b;
  double c2 = l2.c;
  double x = (b1*c2 - b2*c1)/(a1*b2-a2*b1);
  double y = (a1*c2 - a2*c1)/(a2*b1-a1*b2);
  return Pair(x, y);
}

int main() {
  scanf("%d", &n);
  while (n--) {
    for (int i=0; i<3; i++) {
      scanf("%lf%lf", &xs[i], &ys[i]);
    }

    Line l1, l2;
    l1.a = xs[1]-xs[0];
    l1.b = ys[1]-ys[0];
    l1.c = -(xs[1]*xs[1]-xs[0]*xs[0] + ys[1]*ys[1]-ys[0]*ys[0])/2;
    l2.a = xs[1]-xs[2];
    l2.b = ys[1]-ys[2];
    l2.c = -(xs[1]*xs[1]-xs[2]*xs[2] + ys[1]*ys[1]-ys[2]*ys[2])/2;
    Pair p = Intersect(l1, l2);
    double r = Dist(p, Pair(xs[0], ys[0]));
    p.first = int(p.first*1000)/1000.0;
    p.second = int(p.second*1000)/1000.0;
    r = int(r*1000)/1000.0;
    printf("%.3f %.3f %.3f\n", p.first, p.second, r);
  }
}

C++: #include <iostream>

int main(){
  int n;
  double a,b,c,d,e,f;
  double x1,x2,x3,y1,y2,y3;
  double px,py;
  double r;

  cin >> n;

  for(int i=0;i<n;i++){
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    a = (x2-x1)*2.0;
    b = (y2-y1)*2.0;
    c = (x2*x2 + y2*y2 - x1*x1 - y1*y1);
    d = (x3-x1)*2.0;
    e = (y3-y1)*2.0;
    f = (x3*x3 + y3*y3 - x1*x1 - y1*y1);
    px = (c*e-b*f)/(a*e-b*d);
    py = (a*f-c*d)/(a*e-b*d);
    r = sqrt((px-x1)*(px-x1) + (py-y1)*(py-y1));
    printf("%.3f %.3f %.3f\n",px,py,r);



  }

  return 0;
}

C++: #include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#include <string>
#include <cmath>
using namespace std;

int main(){
	double n,a,b,c,d,e,f,x,y,r;
	
	cin >> n ;
	for(int turn=0;turn<n;turn++){
		cin >> a >> b >> c >> d >> e >> f;
		x=((c-a)*(e*e+f*f-a*a-b*b)-(e-a)*(c*c+d*d-a*a-b*b))/(2*((f-b)*(c-a)-(e-a)*(d-b)));
		y=((f-b)*(c*c+d*d-a*a-b*b)-(d-b)*(e*e+f*f-a*a-b*b))/(2*((f-b)*(c-a)-(e-a)*(d-b)));
		
		r=sqrt((x-a)*(x-a)+(y-b)*(y-b));
		
		printf("%.3f %.3f %.3f\n",x,y,r);
	}
return 0;
}

C++: #include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main(){
  double a[2],b[2],c[2],m[2][2],inv[2][2],ans[2],x,y,det,r;
  int n;
  cin >>n;
  while(n--){
    cin >>a[0]>>a[1]>>b[0]>>b[1]>>c[0]>>c[1];
    b[0]-=a[0];
    b[1]-=a[1];
    c[0]-=a[0];
    c[1]-=a[1];
    m[0][0] = 2*b[0];
    m[1][0] = 2*b[1];
    m[0][1] = 2*c[0];
    m[1][1] = 2*c[1];
    ans[0] = b[0]*b[0]+b[1]*b[1];
    ans[1] = c[0]*c[0]+c[1]*c[1];
    det = m[0][0]*m[1][1]-m[0][1]*m[1][0];
    inv[0][0] = m[1][1]/det;
    inv[1][0] = -m[1][0]/det;
    inv[0][1] = -m[0][1]/det;
    inv[1][1] = m[0][0]/det;
    x = ans[0]*inv[0][0]+ans[1]*inv[1][0];
    y = ans[0]*inv[0][1]+ans[1]*inv[1][1];
    r = sqrt(x*x+y*y);
    x+=a[0];
    y+=a[1];
    printf("%.3lf %.3lf %.3lf\n",x,y,r);
  }
  return 0;
}

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

using namespace std;

int main(){
    int cnt;
    cin >> cnt;
    double x1, y1, x2, y2, x3, y3;
    double a1, a2, b1, b2, c1, c2;
    double a, b, c;
    double A;
    double xp, yp, r;
    while(cnt > 0 && 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;
        xp = (double)((b1*c2 - b2*c1)/(a1*b2 - a2*b1)*1000) / 1000.0;
        yp = (double)((c1*a2 - c2*a1)/(a1*b2 - a2*b1)*1000) / 1000.0;

     r=hypot(xp-x1,yp-y1);

        cout << fixed << setprecision(3);
        cout << xp << " " << yp << " " << r << endl;
        cnt -= 1;
    }
    return 0