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: import math
for _ in range(int(input())):
  x1,y1,x2,y2,x3,y3=map(float,input().split())
  a,b,c=2*(x2-x1),2*(y2-y1),x1**2-x2**2+y1**2-y2**2
  aa,bb,cc=2*(x3-x1),2*(y3-y1),x1**2-x3**2+y1**2-y3**2
  x,y=(b*cc-bb*c)/(a*bb-aa*b),(c*aa-cc*a)/(a*bb-aa*b)
  print('%.3f %.3f %.3f'%(x,y,math.hypot(x1-x,y1-y)))

Python: import math

n = int(input())
positions = []
for i in range(n):
  positions.append(list(map(float, input().split())))

for i in range(n):
  ra = [positions[i][0],positions[i][1]]
  rb = [positions[i][2],positions[i][3]]
  rc = [positions[i][4],positions[i][5]]

  A = (rb[0]-rc[0])**2+(rb[1]-rc[1])**2
  B = (rc[0]-ra[0])**2+(rc[1]-ra[1])**2
  C = (ra[0]-rb[0])**2+(ra[1]-rb[1])**2

  P = A * (B+C-A)
  Q = B * (C+A-B)
  R = C * (A+B-C)

  rcc_x = (P*ra[0] + Q*rb[0] + R*rc[0]) / (P+Q+R)
  rcc_y = (P*ra[1] + Q*rb[1] + R*rc[1]) / (P+Q+R)

  radius = math.sqrt((rcc_x-positions[i][0])**2+(rcc_y-positions[i][1])**2)
  print("{0:.3f} {1:.3f} {2:.3f}".format(rcc_x,rcc_y,radius))

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)

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 math

def da(li):
    x1,y1,x2,y2,x3,y3=[float(i) for i in li]
    xp,yp=(x2-x1)/2,(y2-y1)/2
    xq,yq=(x3-x1)/2,(y3-x1)/2
    t=(xq**2+yq**2-xp*xq-yp*yq)/(xp*yq-xq*yp)
    return x1-(xp-t*yp),y1-(yp+t*xp)
def sis(fl):
    fls=str(fl)
    if len(fls)<6:return fls+"".join(["0" for i in range(5-len(fls))])
    if int(fls[5:6])>4:
        return fls[:4]+str(int(fls[4:5])+1)
    else:
        return fls[:5]

n=int(input())
for i in range(n):
    li=input().split(" ")
    x,y=da(li)
    print(sis(x)+" "+sis(y)+" "+sis(math.sqrt(x**2+y**2)))

Python: from math import sqrt 
for _ in range(int(input())) :
    x1, y1, x2, y2, x3, y3 = [float(temp) for temp in input().split()]
    a = [x1, y1, (x1 ** 2) + (y1 ** 2)]
    b = [x2, y2, (x2 ** 2) + (y2 ** 2)]
    c = [x3, y3, (x3 ** 2) + (y3 ** 2)]
    a1 = [(b[0] - a[0]), (b[1] - a[1]), (b[2] - a[2])]
    b1 = [(c[0] - a[0]), (c[1] - a[1]), (c[2] - a[2])]
    a1[1], a1[2] = (a1[1] / a1[0]), (a1[2] / a1[0])
    b1[1], b1[2] = (b1[1] / b1[0]), (b1[2] / b1[0])
    m = -(a1[2] - b1[2]) / (a1[1] - b1[1])
    l = -(a1[1] * m + a1[2])
    n = -((l * a[0]) + (m * a[1]) + a[2])
    px = -l / 2
    py = -m / 2
    r  = sqrt(((l / 2) ** 2)+((m / 2) ** 2)+n)
    print('{:0.3f} {:0.3f} {:0.3f}'.format(px, py, r))