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 <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
using namespace std;

#define FOR(i,a,b) for(long long int i=(a);i<(b);i++)
#define REP(i,n) for(long long int i=0;i<(n);i++)
#define ALL(s) (s).begin(),(s).end()

#define PI 3.14159265358479

typedef long long int ll;
typedef vector<long long int> vi;
typedef vector<long long int>::iterator vit;

void se(double a, double b, double c, double d, double e, double f,double *x,double *y){
	if (a < 0){
		a = -a;
		b = -b;
		c = -c;
	}
	if (b == -0)b = 0;
	if (d < 0){
		d = -d;
		e = -e;
		f = -f;
	}
	cout << a << " " << b << " " << c << " " << d << " " << e << " " << f << "\n";
	if (a == 0){
		*y = c / b;
		*x = (f - e*(*y)) / d;
	}
	else if (b == 0){
		*x = c / a;
		*y = (f - e*(*x)) / d;
	}
	if (d == 0){
		*y = f / e;
		*x = (c - b*(*y)) / a;
	}
	else if (e == 0){
		*x = f / d;
		*y = (c - a*(*x)) / b;
	}
	else if (a != 0 && b != 0 && d != 0 && e != 0){
		*x = (b*f - c*e) / (b*d - a*e);
		*y = (c*d - a*f) / (b*d - a*e);
	}
}


int main(){
	double x1, y1, x2, y2, x3, y3, px, py, r;
	ll n;
	cin >> n;
	REP(i,n){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		se(2.0*(x1 - x2), 2.0*(y1 - y2),
			pow(x1, 2.0) + pow(y1, 2.0) - pow(x2, 2.0) - pow(y2, 2.0),
			2.0*(x2 - x3), 2.0*(y2 - y3),
			pow(x2, 2.0) + pow(y2, 2.0) - pow(x3, 2.0) - pow(y3, 2.0), &px, &py);
		r = pow(pow(x1 - px, 2.0) + pow(y1 - py, 2.0), 0.5);

		printf("%.3lf %.3lf %.3lf", px, py, r);
	}
}

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

int main(){
    int n;
    double x1, x2, x3, y1, y2, y3, x, y;
    cin >> n;
    for(int i = 0;i < n;i++){
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	if(y1 == y2)swap(x1, x3), swap(y1, y3);
	else if(y1 == y3)swap(x1, x2), swap(y1, y2);
	double x = (x3-x1)/(y1-y3)*(x1+x3)/2-(x2-x1)/(y1-y2)*(x1+x2)/2-(y1+y2)/2+(y1+y3)/2;
	x /= ((x3-x1)/(y1-y3) - (x2-x1)/(y1-y2));
	double y = (x2-x1)/(y1-y2)*(x - (x1+x2)/2) + (y1+y2)/2;
	cout << x << " " << y << " " << hypot(x1-x,y1-y) << endl;   
    }
    return 0;
}
/*
x1y1 x2y2
y = (x2-x1)/(y1-y2)*(x - x1+x2/2) + y1+y2/2
y = (x3-x1)/(y1-y3)*(x - x1+x3/2) + y1+y3/2


(x3-x1)/(y1-y3)*(x - x1+x3/2) + y1+y3/2
 = (x2-x1)/(y1-y2)*(x - x1+x2/2) + y1+y2/2
((x3-x1)/(y1-y3) - (x2-x1)/(y1-y2))*x
=
(x3-x1)/(y1-y3)*(x1+x3)/2-(x2-x1)/(y1-y2)*(x1+x2)/2+(y1+y2)/2-(y1+y3)/2

*/

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

int main() {
	int sampleNum;
	scanf("%d", &sampleNum);
	for (; sampleNum > 0; --sampleNum) {
		double x1, y1, x2, y2, x3, y3;
		scanf("%lf %lf %lf %lf %lf %lf", &x1, &y1, &x2, &y2, &x3, &y3);

		double ax = x3 - x2;
		double ay = y3 - y2;
		double a2 = ax * ax + ay * ay;
		double a = sqrt(a2);
		double bx = x1 - x3;
		double by = y1 - y3;
		double b2 = bx * bx + by * by;
		double b = sqrt(b2);
		double cx = x2 - x1;
		double cy = y2 - y1;
		double c2 = cx * cx + cy * cy;
		double c = sqrt(c2);

		double crossabz = ax * by - ay * bx;

		double px, py, r;

		if (crossabz == 0) {
			if (a < b) {
				if (b < c) {
					px = (x1 + x2) / 2.;
					py = (y1 + y2) / 2.;
					r = c / 2.;
				} else {
					px = (x3 + x1) / 2.;
					py = (y3 + y1) / 2.;
					r = b / 2.;
				}
			} else {
				px = (x2 + x3) / 2.;
				py = (y2 + y3) / 2.;
				r = a / 2.;
			}
		} else {
			double bunbo = a2 * a2 - 2. * a2 * (b2 + c2) + (b2 - c2) * (b2 - c2);
			double keisu1 = a2 * (a2 - b2 - c2);
			double keisu2 = b2 * (b2 - c2 - a2);
			double keisu3 = c2 * (c2 - a2 - b2);
			px = (keisu1 * x1 + keisu2 * x2 + keisu3 * x3) / bunbo;
			py = (keisu1 * y1 + keisu2 * y2 + keisu3 * y3) / bunbo;

			double s = fabs(crossabz) / 2.;
			r = a * b * c / (4. * s);
		}

		if ( px <= 0. && px > 5.e-4 ) { px = 0.; }
		if ( py <= 0. && py > 5.e-4 ) { py = 0.; }

		printf("%.3lf %.3lf %.3lf\n", px, py, r);
	}
	return 0;
}