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(void){
	int n, i, j;
	double x1,y1,x2,y2,x3,y3, px, py;
	scanf("%d",&n);
	for(i = 0;i < n;i++){
		scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
		py = ((x3 - x1) * (pow(x2,2.0) - pow(x1,2.0) + pow(y2,2.0) - pow(y1,2.0)) - (x2 - x1) * (pow(x3,2.0) - pow(x1,2.0) + pow(y3,2.0) - pow(y1,2.0))) / (2 * ((y2 - y1) * (x3 - x1) - (y3 - y1) * (x2 - x1)));
		px = ((y3 - y1) * (pow(y2,2.0) - pow(y1,2.0) + pow(x2,2.0) - pow(x1,2.0)) - (y2 - y1) * (pow(y3,2.0) - pow(y1,2.0) + pow(x3,2.0) - pow(x1,2.0))) / (2 * ((x2 - x1) * (y3 - y1) - (x3 - x1) * (y2 - y1)));
		printf("%f %f %f\n",px,py,sqrt(pow(px - x1,2.0) + pow(px - x1,2.0)));
	}
	return 0;
}

C++: #include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
using namespace std;
int main(void){
  int n;
  double x[3],y[3];
  double a[2],b[2],c[2];
  double xa,ya;
  scanf("%d",&n);
  for(int i=0;i<n;i++){
    for(int j=0;j<3;j++){
      scanf("%lf %lf",&x[j],&y[j]);
    }
    for(int j=1;j<3;j++){
      a[j-1]=2*(x[j]-x[0]);
      b[j-1]=2*(y[j]-y[0]);
      c[j-1]=x[0]*x[0]-x[j]*x[j]+y[0]*y[0]-y[j]*y[j];
    }
    xa=(b[0]*c[1]-b[1]*c[0])/(a[0]*b[1]-a[1]*b[0]);
    ya=(c[0]*a[1]-c[1]*a[0])/(a[0]*b[1]-a[1]*b[0]);
    printf("%.3f %.3f %.3f\n",xa,ya,hypot(abs(xa-x[0]),abs(ya-y[0])));
  }
}

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

int main(){
  int n;
  double a,b,c,d,e,f,x,y,r;
  double x1,y1,x2,y2,x3,y3;

  std::cin >> n;

  for(int i=0;i<n;i++){
    std::cin >> x1>>y1>>x2>>y2>>x3>>y3;
    a = 2*(x1-x2);
    b = 2*(y1-y2);
    c = +(x1*x1-x2*x2)+(y1*y1-y2*y2);
    d = 2*(x2-x3);
    e = 2*(y2-y3);
    f = +(x2*x2-x3*x3)+(y2*y2-y3*y3);

    x = (double)(c*e-b*f)/(a*e-b*d);
    y = (double)(a*f-c*d)/(a*e-b*d);

    if(x == 0){x = 0;}
    if(y == 0){y = 0;}

    r = sqrt((x-x1)*(x-x1)+(y-y1)*(y-y1));

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

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

int main(){
	double x[4],y[4],a[3],b[3],c[3],cx[1000],cy[1000],rx,ry,r[1000];
	int i,n,j;
	
	scanf("%d",&n);
	for(j=0;j<n;j++){
	
	for(i=0;i<3;i++)scanf("%lf%lf",&x[i],&y[i]);
	a[0]=2*(x[1]-x[0]);
	b[0]=2*(y[1]-y[0]);
	c[0]=x[0]*x[0]-x[1]*x[1]+y[0]*y[0]-y[1]*y[1];
	a[1]=2*(x[2]-x[0]);
	b[1]=2*(y[2]-y[0]);
	c[1]=x[0]*x[0]-x[2]*x[2]+y[0]*y[0]-y[2]*y[2];
	
	cx[j]=(b[0]*c[1]-b[1]*c[0])/(a[0]*b[1]-a[1]*b[0]);
	cy[j]=(c[0]*a[1]-c[1]*a[0])/(a[0]*b[1]-a[1]*b[0]);
	
	rx=x[0]-cx[j];
	ry=y[0]-cy[j];
	r[j]=sqrt(rx*rx+ry*ry);
	
	}
	
	for(i=0;i<n;i++)printf("%.3f %.3f %.3f\n",cx[i],cy[i],r[i]);
	
	return 0;
}

C++: #include <iostream>
#include<math.h>
#include<cstdio>
using namespace std;
  
int main(){
    double x1,x2,x3,y1,y2,y3,trgr,trgx,trgy,A1,B1,C1,A2,B2,C2;
    int i,n;
    cin>>n;
    for(i=0;i<n;i++){
    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;
     
    trgx=(B1*C2-B2*C1)/(A1*B2-A2*B1);
    trgy=(C1*A2-C2*A1)/(A1*B2-A2*B1);
    trgr=sqrt((trgx-x1)*(trgx-x1)+(trgy-y1)*(trgy-y1));
        printf("%.3lf %.3lf %.3lf\n",trgx,trgy,trgr);
    }
    return 0;
}