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 <stdio.h>
#include <string>
#include <queue>
#include <cmath>

#define int64 long long int

using namespace std;

double round(double x){
	if(x > 0) return floor(x + 0.5);
	else return -1.0 * floor(fabs(x) + 0.5);
}

int main()
{
	int n;
	double x1,y1,x2,y2,x3,y3,x,y,r;
	double det,a1,b1,a2,b2,c1,c2;
	cin >> n;
	for(int i=0; i<n; i++){
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		a1 = 2 * (x1 - x2), b1 = 2 * (y1 - y2);
		a2 = 2 * (x2 - x3), b2 = 2 * (y2 - y3);
		det = a1 * b2 - a2 * b1;
		c1 = (x1*x1 - x2*x2) + (y1*y1 - y2*y2);
		c2 = (x2*x2 - x3*x3) + (y2*y2 - y3*y3);
		x = (a1 * c1 + b1 * c2) / det;
		y = (a2 * c1 + b2 * c2) / det;
		r = sqrt((x - x1)*(x - x1) + (y - y1)*(y - y1));
		x *= 1000, y *= 1000, r *= 1000;
		x = round(x), y = round(y), r = round(r);
		x /= 1000, y /= 1000, r /= 1000;
		if(fabs(x) < 1e-12) x = 0.0;
		if(fabs(y) < 1e-12) y = 0.0;
		printf("%.3f %.3f %.3f\n", x, y, r);
	}
	return 0;
}

C++: #include <stdio.h>
#include <math.h>
#define NOT_E 200

double cequal(double *a,double *b,double *c,double *aa,double *bb,double *cc);
double equal(double a,double b,double c,double aa,double bb,double cc);
double answer(double x1,double x2,double y1,double y2,double *a,double *b);
int swap(double *a,double *b);

int main(){
	int i,cnt;
	double x1,x2,x3,y1,y2,y3,xp,yp/*¦*/,a1,a2,b1,b2,xm1,ym1,xm2,ym2,r;
	
	scanf("%d",&cnt);
	for(i=0;i<cnt;i++){
		
		scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
		
		xp=equal(y1,y2,y3,x1,x2,x3);
		yp=equal(x1,x2,x3,y1,y2,y3);
		
		
		if (xp==NOT_E || yp==NOT_E){
			if(xp==NOT_E){
				cequal(&x1,&x2,&x3,&y1,&y2,&y3);
			}else if(yp==NOT_E){
				cequal(&y1,&y2,&y3,&x1,&x2,&x3);
			}
			answer(x3,x2,y3,y2,&a1,&b1);
			answer(x3,x1,y3,y1,&a2,&b2);
			xp=(b2-b1)/(a1-a2);
			yp=a1*xp+b1;
			
		}
		
		if(xp==x1){
			r=abs(xp-x1);
		}else if(yp==y2){
			r=abs(yp-y1);
		}else{
			r=sqrt((xp-x1)*(xp-x1)+(yp-y1)*(yp-y1));
		}
		
		printf("%.3f %.3f %.3f\n",xp,yp,r);

	}
	return 0;
}
			
			
			
			

double cequal(double *a,double *b,double *c,double *aa,double *bb,double *cc){	/*a1=a2,a3ÆÈéæ¤ÉÀÑÖ¦é*/
	if(*a==*b){
	}else if (*b==*c){
		swap(a,c);
		swap(aa,cc);
	}else if (*c==*a){
		swap(b,c);
		swap(bb,cc);
	}else{
		return NOT_E;
	}
	
	return (*a+*b)/2;
}


double equal(double a,double b,double c,double aa,double bb,double cc){	/*ÀÑÖ¦È¢*/
	if(a==b){
	}else if (b==c){
		swap(&a,&c);
		swap(&aa,&cc);
	}else if (c==a){
		swap(&b,&c);
		swap(&bb,&cc);
	}else{
		return NOT_E;
	}
	return (aa+bb)/2;
}



double answer(double x1,double x2,double y1,double y2,double *a,double *b){	/*(x1,y1)Æ(x2,y2)Ì¼ñªüy=ax+bÌa,bð|C^ÅÔ·*/
	double xm,ym;
	*a=(y2-y1)/(x1-x2);
	xm=(x2+x1)/2;
	ym=(x2+y1)/2;
	*b=ym-*a*xm;
	return 0;
}

int swap(double *a,double *b){
	double temp;
	temp=*a;
	*a=*b;
	*b=*a;
	return 0;
}
	/*
	a2=(y1-y3)/(x3-x1);
	xm2=(x1+x3)/2;
	ym2=(x1+y3)/2;
	b2=ym2-a3*xm2;*/

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

int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    double x1, y1, x2, y2, x3, y3, px, py, r;
    cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
    py = ((x3 - x1) * (x1 * x1 + y1 * y1 - x2 * x2 - y2 * y2) - (x2 - x1) * (x1 * x1 + y1 * y1 - x3 * x3 - y3 * y3)) /
         (2 * (x3 - x1) * (y1 - y2) - 2 * (x2 - x1) * (y1 - y3));
    if (x2 - x1 != 0) {
      px = (2 * (y1 - y2) * py - x1 * x1 - y1 * y1 + x2 * x2 + y2 * y2) / (2 * (x2 - x1));
    } else {
      px = (2 * (y1 - y3) * py - x1 * x1 - y1 * y1 + x3 * x3 + y3 * y3) / (2 * (x3 - x1));
    }
    r = sqrt((px - x1) * (px - x1) + (py - y1) * (py - y1));
    cout << fixed << setprecision(3) << px << " " << py << " " << r << endl;
  }
  return 0;
}