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<stdio.h>
#include<math.h>
double x1, y1, x2, y2, x3, y3;
double px, py;
int main()
{
    int n;
    scanf("%d",&n);
    while(n--)
    {
        scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
        double A1 =(x2*x2+y2*y2-x1*x1-y1*y1)*(y3-y1);
        double B1 =(x3*x3+y3*y3-x1*x1-y1*y1)*(y2-y1);
        double A2 =(x3*x3+y3*y3-x1*x1-y1*y1)*(x2-x1);
        double B2 =(x2*x2+y2*y2-x1*x1-y1*y1)*(x3-x1);
        double D = (x2-x1)*(y3-y1)-(y2-y1)*(x3-x1);
        double X=(A1-B1)/D/2;
        double Y=(A2-B2)/D/2;
        double R = sqrt((X-x1)*(X-x1)+(Y-y1)*(Y-y1));
        printf("%.3f %.3f %.3f\n",X,Y,R);
    }
    return 0;
}

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

using namespace std;

typedef complex<double> point;
#define X real()
#define Y imag()
typedef point vec;

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

double dis(point a, point b)
{ return abs(a - b); }

point center(point A, point B, point C) // Circumcenter
{
	B -= A; C -= A;
	double b = norm(B), c = norm(C), d = 2 * cross(B, C);
	return A + point(C.Y * b - B.Y * c, B.X * c - C.X * b) / d;
}

int main()
{
	int dat;
	scanf("%d", &dat);
	while (dat--) {
		point p[3], c;
		for (int i = 0; i < 3; ++i) {
			double x, y;
			scanf("%lf%lf", &x, &y);
			p[i] = point(x, y);
		}
		c = center(p[0], p[1], p[2]);
		printf("%.3lf %.3lf %.3lf\n", c.X, c.Y, dis(c, p[0]));
	}
}

C++: #include<iostream>
#include<math.h>
#include<vector>
#include<algorithm>
using namespace std;

int main()
{
   int n;
   cin>>n;
   while(n--){
       double x1,x2,x3,y1,y2,y3;
       double px,py,r;
       scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
       double a1=(x2*x2+y2*y2-x1*x1-y1*y1)*(y3-y1);
       double b1 =(x3*x3+y3*y3-x1*x1-y1*y1)*(y2-y1);
        double a2 =(x3*x3+y3*y3-x1*x1-y1*y1)*(x2-x1);
        double b2 =(x2*x2+y2*y2-x1*x1-y1*y1)*(x3-x1);
        double c = (x2-x1)*(y3-y1)-(y2-y1)*(x3-x1);
        px=(a1-b1)/c/2;
        py=(a2-b2)/c/2;
        r = sqrt((px-x1)*(px-x1)+(py-y1)*(py-y1));
        printf("%.3f %.3f %.3f\n",px,py,r);
   }
    return 0;
}

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

int main(){
    int n;
    cin>>n;
    while(n--){
        float x1,y1,x2,y2,x3,y3;
        cin>>x1>>y1>>x2>>y2>>x3>>y3;
        float p1,p2,p3;
        p1 = (max((fabs(x1 - x2),fabs(x1 - x3)),fabs(x2 - x3))) / 2.000;
        p2 = (max((fabs(y1 - y2),fabs(y1 - y3)),fabs(y2 - y3))) / 2.000;
        p3 = sqrt((p1 - x1) * (p1 - x1) + (p2 - y1) * (p2 - y1));
        printf("%4.3f %4.3f %4.3f",p1,p2,p3);
    }
    return 0;
}

C++: #include<iostream>
#include<cmath>
#include<algorithm>
#include<iomanip>
using namespace std;
class Point {
public:
	double x, y;
};
double distance(Point x, Point y) {
	return pow(pow(fabs(x.x - y.x), 2) + pow(fabs(x.y - y.y), 2), 0.5);
}
int main() {
	cout << setprecision(4);
	int n;
	cin >> n;
	for (int i = 0; i < n; i++) {
		Point p[3], s;
		for (int i = 0; i < 3; i++) {
			cin >> p[i].x >> p[i].y;
		}
		double a, b, c, d, e, f;
		a = (-2)*p[0].x + 2 * p[1].x;
		b = (-2)*p[0].y + 2 * p[1].y;
		c = (-2)*p[0].x + 2 * p[2].x;
		d = (-2)*p[0].y + 2 * p[2].y;
		e = pow(p[0].x, 2) + pow(p[0].y, 2) - pow(p[1].x, 2) - pow(p[1].y, 2);
		f = pow(p[0].x, 2) + pow(p[0].y, 2) - pow(p[2].x, 2) - pow(p[2].y, 2);
		s.x = (b*f - d*e) / (a*d - b*c);
		s.y = (a*f - c*e) / (b*c - a*d);
		double k = distance(p[0], s);
		s.x = round(s.x * 1000) / 1000;
		s.y = round(s.y * 1000) / 1000;
		k = round(k * 1000) / 1000;
		cout << s.x << " " << s.y << " " << k << endl;
	}
	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

int n;
double xa, ya, xb, yb, xc, yc, x, y, r;

signed main() {
	cin >> n;
	for(int i=0; i<n; i++) {
		cin >> xa >> ya >> xb >> yb >> xc >> yc;
		x = ((ya-yb)*(xc*xc+yc*yc-xa*xa-ya*ya)-(ya-yc)*(xb*xb+yb*yb-xa*xa-ya*ya))/(2*((ya-yc)*(xa-xb)-(ya-yb)*(xa-xc)));
		y = ((xa-xb)*(xc*xc+yc*yc-xa*xa-ya*ya)-(xa-xc)*(xb*xb+yb*yb-xa*xa-ya*ya))/(2*((ya-yb)*(xa-xc)-(ya-yc)*(xa-xb)));
		r = sqrt((x-xa)*(x-xa)+(y-ya)*(y-ya));
		printf("%.3lf %.3lf %.3lf\n",x,y,r);
	}
}