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))
	}
}

Python: #!/usr/bin/env python
from math import *
def g(x):
	y = (int((1000 * abs(x)) * 2 + 1) // 2) / 1000
	if x < 0:
		y *= -1
	return y
def func(x):
	x1, y1, x2, y2, x3, y3 = x
	
	a = x1 - x2
	b = y1 - y2
	c = (x1 * x1 + y1 * y1 - x2 * x2 - y2 * y2) / 2
	d = x1 - x3
	e = y1 - y3
	f = (x1 * x1 + y1 * y1 - x3 * x3 - y3 * y3) / 2
	x = (e * c - b * f) / (a * e - b * d)
	y = (a * f - d * c) / (a * e - b * d)
	r = sqrt((x1 - x) * (x1 - x) + (y1 - y) * (y1 - y))
	x = "{0:.3f}".format(g(x))
	y = "{0:.3f}".format(g(y))
	r = "{0:.3f}".format(g(r))
	print(x + " " + y + " " + r)
n = int(input())
a = []
for _ in range(n):
	a.append(list((map(float, input().split()))))
for i in a:
	func(i)

Python: import sys
import math

def to_f(e):
  return float(e)

n = int(raw_input().rstrip())
for i in range(n):
  line = raw_input().rstrip() 
  x1, y1, x2, y2, x3, y3 = map(to_f, line.split(" "))
  a1 = 2*(x2-x1)
  a2 = 2*(x3-x1)
  b1 = 2*(y2-y1)
  b2 = 2*(y3-y1)
  c1 = x1**2-x2**2+y1**2-y2**2
  c2 = x1**2-x3**2+y1**2-y3**2
  xp = (b1*c2-b2*c1)/(a1*b2-a2*b1)
  yp = (c1*a2-c2*a1)/(a1*b2-a2*b1)
  r  = math.sqrt((xp-1)**2+(yp-y1)**2)
  print("{0:.3f} {0:.3f} {0:.3f}".format(xp, yp, r))

Python: n = int(input())
for i in range(n):
    x1, y1, x2, y2, x3, y3 = list(map(float, input().split()))
    a = 2*(x1-x2)
    b = 2*(y1-y2)
    c = x1**2 - x2**2 + y1**2 - y2**2
    d = 2*(x1-x3)
    e = 2*(y1-y3)
    f = x1**2 - x3**2 + y1**2 - y3**2

    y = (c*d - a*f) / (b*d - a*e)
    if a==0:
        x = (f - e*y) / d
    else:
        x = (c - b*y) / a
    
    r = ((x1 - x)**2 + (y1 - y)**2)**0.5
    print('{:.3f}'.format(round(x, 3)), end=" ")
    print('{:.3f}'.format(round(y, 3)), end=" ")
    print('{:.3f}'.format(round(r, 3)))

Python: # -*- coding: utf-8 -*-

import cmath

class Point(object):
    def __init__(self, x, y):
        self.point = complex(x, y)
    def __str__(self):
        return "x = {0}, y = {1}".format(self.point.real, self.point.imag)

class Triangle(Point):
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c
        # ３辺の長さ
        self.edgeA = abs(b.point-c.point)
        self.edgeB = abs(c.point-a.point)
        self.edgeC = abs(a.point-b.point)
        # ３角の大きさ
        self.angleA = Triangle.angle(self.edgeA, self.edgeB, self.edgeC)
        self.angleB = Triangle.angle(self.edgeB, self.edgeC, self.edgeA)
        self.angleC = Triangle.angle(self.edgeC, self.edgeA, self.edgeB)

    # 角度を求める
    def angle(A, B, C):
        return cmath.acos( (B*B+C*C-A*A)/(2*B*C) )


    # 外接円の半径
    def circumscribedCircleRadius(self):
        return abs((self.edgeA/cmath.sin(self.angleA))/2)

    # 外心
    def circumscribedCircleCenter(self):
        A = cmath.sin(2*self.angleA)
        B = cmath.sin(2*self.angleB)
        C = cmath.sin(2*self.angleC)
        X = (self.a.point.real*A + self.b.point.real*B + self.c.point.real*C) / (A+B+C)
        Y = (self.a.point.imag*A + self.b.point.imag*B + self.c.point.imag*C) / (A+B+C)
        return complex(X, Y)

n = int(input())
for i in range(n):
    line = list(map(float, input().split()))
    p1 = Point(line[0], line[1])
    p2 = Point(line[2], line[3])
    p3 = Point(line[4], line[5])
    T = Triangle(p1, p2, p3)
    center = T.circumscribedCircleCenter()
    print("{0:.4f} {1:.4f} {2:.4f}".format(center.real, center.imag, T.circumscribedCircleRadius()))

Python: import fractions


def calc(x1, y1, x2, y2):
    return 2 * (x2 - x1), 2 * (y2 - y1), x2 ** 2 + y2 ** 2 - x1 ** 2 - y1 ** 2


n = int(input())
for _ in range(n):
    x1, y1, x2, y2, x3, y3 = map(float, input().split())
    cx1, cy1, z1 = calc(x1, y1, x2, y2)
    cx2, cy2, z2 = calc(x1, y1, x3, y3)
    gcd = fractions.gcd(cx1, cx2)
    r1, r2 = cx2 // gcd, cx1 // gcd
    dcy = r1 * cy1 - r2 * cy2
    dz = r1 * z1 - r2 * z2
    y = dz / dcy
    try:
        x = (z1 - cy1 * y) / cx1
    except ZeroDivisionError:
        x = (z2 - cy2 * y) / cx2
    r = ((x - x1) ** 2 + (y - y1) ** 2) ** 0.5
    print(*map(lambda x: '{:.3f}'.format(round(x, 3)), (x, y, r)))