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>

int main()
{
	int n;
	double x1,y1,x2,y2,x3,y3,xp,xp1,xp2,yp1,yp2,yp,r;
	scanf("%d",&n);

	for(int x=0;x<n;x++)
	{
		scanf("%lf %lf %lf %lf %lf %lf",&x1,&y1,&x2,&y2,&x3,&y3);
		xp1=(y1-y3)*(y1*y1 -y2*y2 +x1*x1 -x2*x2) -(y1-y2)*(y1*y1 -y3*y3 +x1*x1 -x3*x3);
		xp2=2*(y1-y3)*(x1-x2)-2*(y1-y2)*(x1-x3);
		xp=xp1/xp2;
		yp1=(x1-x3)*(x1*x1 -x2*x2 +y1*y1 -y2*y2) -(x1-x2)*(x1*x1 -x3*x3 +y1*y1 -y3*y3);
		yp2=2*(x1-x3)*(y1-y2)-2*(x1-x2)*(y1-y3);
		yp=yp1/yp2;

		r=(x3-xp)*(x3-xp)+(y3-yp)*(y3-yp);
		r=sqrt(r);
		printf("%.3f %.3f %.3f",xp+0,yp+0,r+0);
	}
	return 0;
}

C++: //
//  main.cpp
//  CppTest
//
//  Created by Ryu on 2017/02/08.
//  Copyright ?? 2017??´ Ryu. All rights reserved.
//

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

int main(int argc, const char * argv[]) {
    // insert code here...
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int n = 0;
    cin >> n;
    
    float cx[n], cy[n], R[n];
    
    float x[3];
    float y[3];
    float alp[6];
    float d;
    for (int i = 0; i < n; i++) {
        cin >> x[0] >> y[0] >> x[1] >> y[1] >> x[2] >> y[2];
        alp[0] = x[1] - x[0];
        alp[1] = y[1] - y[0];
        alp[2] = alp[0] * (x[0] + x[1]) / 2 + alp[1] * (y[0] + y[1]) / 2;
        alp[3] = x[2] - x[0];
        alp[4] = y[2] - y[0];
        alp[5] = alp[3] * (x[0] + x[2]) / 2 + alp[4] * (y[0] + y[2]) / 2;
        for (int j = 0; j < 6; j++) {
            //printf("%d = %f, ", j, alp[j]);
        }
        d = alp[0] * alp[4] - alp[1] * alp[3];
        //printf("d = %f\n", d);
        cx[i] = (alp[4] * alp[2] - alp[1] * alp[5]) / d;
        cy[i] = (0 - alp[3] * alp[2] + alp[0] * alp[5]) / d;
        R[i] = pow(pow(x[0] - cx[i], 2) + pow(y[0] - cy[i], 2), 0.5);
        if(cx[i] == -0){
            cx[i] = 0;
        }
        if (cy[i] == -0) {
            cy[i] = 0;
        }
        printf("%.3f %.3f %.3f", cx[i], cy[i], R[i]);
    }
    
    
    
    return 0;
}

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

struct h{
	double l;
	double m;
	double n;
	double k;
};

void getl(h *len, const double x, const double y){
	len->l = x;
	len->m = y;
	len->n = 1.0;
	len->k = -(x*x + y*y);
}

void calc(h *len, double *xp, double *yp, double *r){
	struct h th;

	for(int i=0;i<3; ++i){
		if(len[i].l != 0.0){
			if(i != 0){
				th = len[i];
				len[i] = len[0];
				len[0] = th;
			}
			len[0].m /= len[0].l;
			len[0].n /= len[0].l;
			len[0].k /= len[0].l;
			len[0].l = 1.0;
			break;
		}
	}
	for(int i=1;i<3;++i){
		if(len[i].l != 0.0){
			len[i].m -= len[0].m*len[i].l;
			len[i].n -= len[0].n*len[i].l;
			len[i].k -= len[0].k*len[i].l;
			len[i].l = 0.0;
		}
	}

	for(int i=1; i<3; ++i){
		if(len[i].m != 0.0){
			if(i != 1){
				th = len[i];
				len[i] = len[1];
				len[1] = th;
			}
			len[1].n /= len[1].m;
			len[1].k /= len[1].m;
			len[1].m = 1.0;
			break;
		}
	}
	if(len[0].m != 0.0){
		len[0].n -= len[1].n*len[0].m;
		len[0].k -= len[1].k*len[0].m;
		len[0].m = 0.0;
	}
	if(len[2].m != 0.0){
		len[2].n -= len[1].n*len[2].m;
		len[2].k -= len[1].k*len[2].m;
		len[2].m = 0.0;
	}

	if(len[2].n != 1.0){
		len[2].k /= len[2].n;
		len[2].n = 1.0;
	}
	if(len[0].n != 0.0){
		len[0].k -= len[2].k*len[0].n;
		len[0].n = 0.0;
	}
	if(len[1].n != 0.0){
		len[1].k -= len[2].k*len[1].n;
		len[1].n = 0.0;
	}
	*xp = -len[0].k / 2;
	*yp = -len[1].k / 2;
	*r  = (*xp)*(*xp) + (*yp)*(*yp) - len[2].k;
	*r = sqrt(*r);

	*xp = floor((*xp * 1000 + 0.5))/1000;
	*yp = floor((*yp * 1000 + 0.5))/1000;
	*r = floor((*r * 1000 + 0.5))/1000;
}

int main(void){
	int n=0;
	double x[6];
	double xp,yp,r;
	struct h len[3];

	scanf("%d", &n);
	for(int i=0;i<n;++i){
		scanf("%lf %lf %lf %lf %lf %lf", x, x+1, x+2, x+3, x+4, x+5);
		getl(len  , x[0], x[1]);
		getl(len+1, x[2], x[3]);
		getl(len+2, x[4], x[5]);
		calc(len, &xp, &yp, &r);
		printf("%.3f %.3f %.3f\n", xp, yp, r);
	}
	return 0;
}