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;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a,b) (abs((a) - (b)) < EPS)
#define EQV(a,b) ( EQ((a).X, (b).X) && EQ((a).Y, (b).Y) )
#define LE(n, m) ((n) < (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))

#define fr first
#define sc second

double dot(P a, P b) {
    return (a.X * b.X + a.Y * b.Y);
}
double cross(P a, P b) {
    return (a.X * b.Y - a.Y * b.X);
}

int ccw(P a, P b, P c) {
    b -= a; c -= a;
    if( cross(b,c) > EPS ) return +1;
    if( cross(b,c) < -EPS ) return -1;
    if( dot(b,c) < 0 ) return +2;
    if( norm(b) < norm(c) ) return -2;
    return 0;
}

P crossp_ll(P a1, P a2, P b1, P b2) {
    double d1 = cross(b2-b1, b1-a1);
    double d2 = cross(b2-b1, a2-a1);
    if( EQ(d1,0) && EQ(d2,0) ) return a1; // same line
    if( EQ(d2,0) ) assert(false); // precondition not satisfied
    return a1 + d1 / d2 * (a2 - a1);
}

// ????§???¢??????????????? a, b, c ???????????????????????£??????????????????
P circumcenter(P a, P b, P c) {
    a = (a-c) * 0.5;
    b = (b-c) * 0.5;
    return c + crossp_ll(a, a*P(1,1), b, b*P(1,1));
}

int main() {
    int n; cin >> n;
    for(int i=0; i<n; i++) {
        P a, b, c;
        cin >> a.X >> a.Y >> b.X >> b.Y >> c.X >> c.Y;

        double x = abs(a-b), y = abs(b-c) , z = abs(c-a);
        double cos = (x * x + y * y - z * z) / (2 * x * y);
        double sin = sqrt(1 - cos * cos);
        double r = z / sin / 2;

        P s = circumcenter(a,b,c);
        s.X = round(s.X * 1000) / 1000;
        s.Y = round(s.Y * 1000) / 1000;
        r = round(r * 1000) / 1000;
        printf("%.3f %.3f %.3f\n",s.X, s.Y, r);
    }
    return 0;
}

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

using namespace std;

int main(void){

  int n;
  cin >> n;

  while(n--){

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

    double A1 = 2*(x2 - x1);
    double B1 = 2*(y2 - y1);
    double C1 = pow( x1 , 2 ) - pow( x2 , 2 ) + pow( y1 , 2 ) - pow( y2 , 2);
    double A2 = 2*(x3 - x1);
    double B2 = 2*(y3 - y1);
    double C2 = pow( x1 , 2 ) - pow( x3 , 2 ) + pow( y1 , 2 ) - pow( y3 , 2);
    double x = ( B1*C2 - B2*C1 ) / ( A1*B2 - A2*B1 );
    double y = ( C1*A2 - C2*A1 ) / ( A1*B2 - A2*B1 );
  
  double R = pow( (x - x1) , 2 ) + pow( (y - y1 ) , 2 );
  printf("%.3f %.3f %.3f", x, y, sqrt(R));
  cout << endl;
  }
  return 0;
}

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

using namespace std;

typedef double Real;

Real EPS = 1e-8;

int sgn(Real a, Real b=0){return a<b-EPS?-1:a>b+EPS?1:0;}
Real sqr(Real a){return sqrt(max(a,(Real)0));}

struct Point{
  Real add(Real a, Real b){
    if(abs(a+b) < EPS*(abs(a)+abs(b)))return 0;
    return a+b;
  }
  Real x, y;
  Point(){}
  Point(Real x,Real y) : x(x) , y(y){}

  Point operator + (Point p){return Point(add(x,p.x), add(y,p.y));}
  Point operator - (Point p){return Point(add(x,-p.x), add(y,-p.y));}
  Point operator * (Real d){return Point(x*d,y*d);}
  Point operator / (Real d){return Point(x/d,y/d);}
  Real norm(){return sqr(x*x+y*y);}
  Real dist(Point a){return (*this-a).norm();}
  Real dot(Point a){return x*a.x+y*a.y;}
  Real cross(Point a){return x*a.y-y*a.x;}
};

struct circle{
  Point p;
  Real r;
  circle(){}
  circle(Point p, Real r) : p(p) , r(r){}
};

circle circumscribed_circle(Point p, Point q, Point r){
  Point a,b,c;
  circle res;
  a=(q-p)*2;
  b=(r-p)*2;
  c.x=p.dot(p)-q.dot(q);  
  c.y=p.dot(p)-r.dot(r);

  //c.x=p.x*p.x-q.x*q.x+p.y*p.y-q.y*q.y;
  //c.y=p.x*p.x-r.x*r.x+p.y*p.y-r.y*r.y;

  res.p.x=a.y*c.y-b.y*c.x;
  res.p.y=b.x*c.x-a.x*c.y;
  res.p=res.p/a.cross(b);
  return circle(res.p, p.dist(res.p));
}

int main(void){
  int n;
  cin >> n;
  while(n--){
    vector<Point>v(3);
    for(int i=0;i<3;i++)
      cin >> v[i].x >> v[i].y;

    circle res=circumscribed_circle(v[0],v[1],v[2]);
    //cout << res.p.x << " " << res.p.y << " " << res.r << endl;
    printf("%.3f %.3f %.3f",res.p.x,res.p.y,res.r);
    cout << endl;
  }
  
  return 0;
}