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 <cmath>
#include <iostream>
#include <stdio.h>
using namespace std;

int main() {
  int n;
  double x1,y1,x2,y2,x3,y3,p,p1,p2,q,q1,q2,r;
  cin >> n;
  for(int i=0;i<n;i++) {
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    p1 = (x2 * x2 - x1 * x1 + y2 * y2 - y1 * y1) * (y3 - y1) - (x3 * x3 - x1 * x1 + y3 * y3 - y1 * y1) * (y2 - y1);
    p2 = 2 * (x1 * y2 - x1 * y3 + x2 * y3 - x2 * y1 + x3 * y1 - x3 * y2);
    p = p1 / p2;
    q1 = (y2 * y2 - y1 * y1 + x2 * x2 - x1 * x1) * (x3 - x1) - (y3 * y3 - y1 * y1 + x3 * x3 - x1 * x1) * (x2 - x1);
    q2 =  2 * (y1 * x2 - y1 * x3 + y2 * x3 - y2 * x1 + y3 * x1 - y3 * x2);
    q = q1 / q2;
    r = sqrt((x1-p) * (x1-p) + (y1-q) * (y1-q) );
    p *= 1000;
    p += 0.5;
    p = floor(p);
    p /= 1000;
    q *= 1000;
    q += 0.5;
    q = floor(q);
    q /= 1000;
    r *= 1000;
    r += 0.5;
    r = floor(r);
    r /= 1000;
    printf("%.3f %.3f %.3f\n", p, q, r);
  }
}

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

using namespace std;

int main() {
    int n, x1, y1, x2, y2, x3, y3;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        double a1 = 2 * (x2 - x1), a2 = 2 * (x3 - x1),
               b1 = 2 * (y2 - y1), b2 = 2 * (y3 - y1),
               c1 = x1 * x1 - x2 * x2 + y1 * y1 - y2 * y2,
               c2 = x1 * x1 - x3 * x3 + y1 * y1 - y3 * y3,
               px = (b1 * c2 - b2 * c1) / (a1 * b2 - a2 * b1),
               py = (c1 * a2 - c2 * a1) / (a1 * b2 - a2 * b1),
               r = sqrt(pow(x1 - px, 2) + pow(y1 - py, 2));
        printf("%.3f %.3f %.3f\n", px, py, r);
    }
    return 0;
}

C++: #include<iostream>
#include<stdio.h>
#include<math.h>
using namespace std;
struct Point{double x,y;};
double dis(Point a,Point b){
  return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
Point tri(Point a, Point b, Point c){
  double a1,a2,b1,b2,c1,c2;
  a1=2*(b.x-a.x);
  b1=2*(b.y-a.y);
  c1=a.x*a.x-b.x*b.x+a.y*a.y-b.y*b.y;
  a2=2*(c.x-a.x);
  b2=2*(c.y-a.y);
  c2=a.x*a.x-c.x*c.x+a.y*a.y-c.y*c.y;
  Point p;
  p.x=(b1*c2-b2*c1)/(a1*b2-a2*b1);
  p.y=(c1*a2-c2*a1)/(a1*b2-a2*b1);
  return p;
}
int main(){
  int n;cin >> n;int i;
  for(i=0;i<n;i++){
  Point a,b,c;cin >> a.x >> a.y >> b.x >> b.y >> c.x >> c.y;
  Point x = tri(a,b,c);
  printf("%.3f %.3f %.3f\n",x.x,x.y,dis(x,a));
  }
}

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

int main() {
	int num;
	double x1,y1,x2,y2,x3,y3,px,py,r;
	cin>>num;
	while(num--){
		cin>>x1>>y1>>x2>>y2>>x3>>y3;
		px=((y1-y3)*(y1*y1 -y2*y2 +x1*x1 -x2*x2) -(y1-y2)*(y1*y1 -y3*y3 +x1*x1 -x3*x3)) / (2*(y1-y3)*(x1-x2)-2*(y1-y2)*(x1-x3));
		py=((x1-x3)*(x1*x1 -x2*x2 +y1*y1 -y2*y2) -(x1-x2)*(x1*x1 -x3*x3 +y1*y1 -y3*y3)) / (2*(x1-x3)*(y1-y2)-2*(x1-x2)*(y1-y3));
		r=sqrt(pow((x1-px),2.0)+pow((y1-py),2.0));
		printf("%.3f %.3f %.3f\n",px,py,r);
	}	
	return 0;
}

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

int main(void)
{
double  x1,x2,x3,y1,y2,y3,x,y ,r ,a   ;

while(scanf("%lf%lf%lf%lf%lf%lf",&x1,&x2,&x3,&y1,&y2,&y3)!=EOF){
a=(x1*x1+x2*x2-x3*x3)/2*x1*x2;
r=x3/(2*sin(double a));

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

struct Zahyou
{
	float x, y;
};
Zahyou de[4];

int main()
{
	int n;

	scanf("%d", &n);
	for (int i = 0; i < n; i++)
	{
		for (int j = 1; j < 4; j++)
		{
			scanf("%f %f", &de[j].x, &de[j].y);
		}
		de[0].x = ((de[1].y - de[3].y)*(pow(de[1].y, 2) - pow(de[2].y, 2) + pow(de[1].x, 2) - pow(de[2].x, 2)) + (de[1].y - de[2].y)*(pow(de[1].y, 2) - pow(de[3].y, 2) + pow(de[1].x, 2) - pow(de[3].x, 2))) / (2 * (de[1].y - de[3].y)*(de[1].x - de[2].x) + 2 * (de[1].y - de[2].y)*(de[1].x - de[3].x));
		de[0].y = ((de[1].x - de[3].x)*(pow(de[1].x, 2) - pow(de[2].x, 2) + pow(de[1].y, 2) - pow(de[2].y, 2)) + (de[1].x - de[2].y)*(pow(de[1].x, 2) - pow(de[3].x, 2) + pow(de[1].y, 2) - pow(de[3].y, 2))) / (2 * (de[1].x - de[3].x)*(de[1].y - de[2].y) + 2 * (de[1].x - de[2].x)*(de[1].y - de[3].y));
		
		printf("%.3f %.3f %.3f\n",de[0].x,de[0].y,sqrt(de[0].x+de[0].y));
	}
	return 0;
}