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 <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()

using namespace std;

typedef long long ll;
typedef pair<double, double> P;
typedef pair<double,P> dP;

dP calc_eq (double xa, double ya, double xb, double yb )
{
	double a = (xb - xa );
	double b = (yb - ya );
	double c = (xb - xa)*(xb + xa )/2. + (yb - ya)*(yb+ya )/2.;

	return dP (a, P (b, c ) );		
}

double calc_radius (int xa, int ya, int xb, int yb )
{
	double res = (xa - xb)*(xa - xb) + (ya - yb)*(ya - yb );

	return sqrt (res );
}

int main()
{
//	cut here before submit 
//	freopen ("testcase.CCT", "r", stdin );
	int n;
	cin >> n;
	rep (i, n ){
		double x1, y1, x2, y2, x3, y3;
		cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
		dP l1 = calc_eq (x1, y1, x2, y2 );
		dP l2 = calc_eq (x1, y1, x3, y3 );

		double a = l1.first, b = l1.second.first, c = l1.second.second;
		double d = l2.first, e = l2.second.first, f = l2.second.second;
/*
		cerr << "a: " << a << " b: " << b << " c: " << c << endl;
		cerr << "d: " << d << " e: " << e << " f: " << f << endl;
*/
		double x = 0.0, y = 0.0, r = 0.0;
		x = (c*e - b*f)/(a*e - b*d);
		y = (c*d - a*f)/(b*d - a*e);
		r = calc_radius (x, y, x1, y1 );

		if (fabs(x) < 1.0e-3){
			x = 0.0;
		} // end if
		if (fabs(y) < 1.0e-3){
			y = 0.0;
		} // end if

		printf ("%.3f %.3f %.3f\n", x, y, r );

	} // end loop

//	printf ("%d\n", res );
		
	return 0;
}

C++: #include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
#include <string>
#include <functional>
#include <array>
#include <stack>
#include <queue>
#include <chrono>
#include <numeric>
#include <memory.h>
#include <map>
#include <math.h>
#include <utility>


#pragma warning(disable:4996)
using namespace std;
#define REP(i,n) for(int i = 0 ; i < n ; ++i)
typedef long long Int;
const double PI = 3.141592653589793238;
const Int INF = 999999999999;
typedef pair<int, int> P;


double A[2][2];
double C[2];


int main()
{
	int n;
	cin >> n;
	REP(i, n){
		double x1, x2, x3, y1, y2, y3;
		cin >> x1>> x2 >> x3 >> y1 >> y2 >> y3;

		double x21 = x2 - x1;
		double x31 = x3 - x1;
		double y21 = y2 - y1;
		double y31 = y3 - y1;

		double xc = ((y31*(x21*x21 + y21*y21)) - (y21*(x31*x31 + y31*y31))) /
			(2 * (x21*y31 - y21*x31));

		double yc = ((x21*(x31*x31 + y31*y31)) - (x31*(x21*x21 + y21*y21))) /
			(2 * (x21*y31 - y21*x31));	
		
		double d = (xc - x1)*(xc - x1) + (yc - y1)*(yc - y1);
		int xc_ = xc * 1000;
		int yc_ = yc * 1000;
		xc_ += (xc_ % 10) > 4 ? 1 : 0;
		yc_ += (yc_ % 10) > 4 ? 1 : 0;

		printf("%.3lf %.3lf %.3lf", xc, yc, sqrt(d));


	}

}

C++: int main(){
	double x1 , y1 , x2 , y2 , x3 , y3;
	double a1 , b1 , c1 , a2 , b2 , c2;
	double a , b , c;
	double px , py , r;
	double tmp;
	cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3;
	a1=2*(x2-x1);
	b1=2*(y2-y1);
	c1=x1*x1-x2*x2+y1*y1-y2*y2;
	a2=2*(x3-x1);
	b2=2*(y3-y1);
	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);
	a=sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
	b=sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));
	c=sqrt((x3-x1)*(x3-x1)+(y3-y1)*(y3-y1));
	//(a/(2*r))*(a/(2*r))+((b*b-c*c-2a)/2*b*c)*((b*b-c*c-2a)/2*b*c)=1
	r=a/(2*sqrt(1-((b*b+c*c-a*a)/(2*b*c))*((b*b+c*c-a*a)/(2*b*c))));
	tmp=px*1000+0.5;
	px=(int)tmp;
	px/=1000;
	tmp=px*1000+0.5;
	py=(int)tmp;
	py/=1000;
	tmp=r*1000+0.5;
	r=(int)tmp;
	r/=1000;
	cout << fixed << setprecision(3) << px << " " << py << " " << r << endl;
	return 0;
}