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: from math import sqrt
n = int(input())
for i in range(n):
    x1,y1,x2,y2,x3,y3 = list(map(float, input().split()))
    c = 2*((x2 - x1)*(y3 - y1) - (y2 - y1)*(x3 - x1))
    ox = ((y3 - y1)*(x2**2 - x1**2 + y2**2 - y1**2) + (y1 - y2)*(x3**2 - x1**2 + y3**2 - y1**2))/c
    oy = ((x1 - x3)*(x2**2 - x1**2 + y2**2 - y1**2) + (x2 - x1)*(x3**2 - x1**2 + y3**2 - y1**2))/c
    r = sqrt((x1-ox)**2+(y1-oy)**2)
    print("{0:.3f} {1:.3f} {2:.3f}".format(ox+0.0, oy+0.0, r+0.0))

Python: #!/usr/bin/python
import sys,math
if sys.version_info[0]>=3: raw_input=input
N=int(raw_input())
for i in range(N):
	x1,y1,x2,y2,x3,y3=[float(e) for e in raw_input().split()]
	a1=2*x2-2*x1
	b1=2*y2-2*y1
	c1=x1*x1-x2*x2+y1*y1-y2*y2
	a2=2*x3-2*x1
	b2=2*y3-2*y1
	c2=x1*x1-x3*x3+y1*y1-y3*y3
	x=(b1*c2-b2*c1)/(a1*b2-a2*b1)
	y=(c1*a2-c2*a1)/(a1*b2-a2*b1)
	print('%.3f %.3f %.3f'%(x,y,math.hypot(x1-x,y1-y)))

Python: import math
n = int(input())
i = 0
while i < n:
   x1, y1, x2, y2, x3, y3 = map(float,input().split())
   a = x2 - x1
   b = y2 - y1
   c = x3 - x1
   d = y3 - y1
   e = a * (x1 + x2) + b * (y1 + y3)
   f = c * (x1 + x2) + d * (y1 + y3)
   g = 2.0 * (a * (y3 - y2) - b * (x3 - x2))
   if g == 0:
       exit()
   px = (d * e - b * f) / g
   py = (a * f - c * e) / g
   radius = ( (py - y1)*(py - y1) + (px - x1)*(px - x1) )
   print("%.3f %.3f %.3f"%(px,py,math.sqrt(radius)))

Python: # AOJ 0010 Circumscribed Circle of a Triangle
# Python3 2018.6.22 bal4u

import math
EPS = 1e-8

def cross(a, b):
	return a.real*b.imag - a.imag*b.real
def dist(a, b):
	return math.hypot(a.real-b.real, a.imag-b.imag)
	
# 両直線の交点
def crossPointLL(ln1, ln2):
	u = ln1[1]-ln1[0]
	v = ln2[1]-ln2[0]
	return ln1[0] + u*(cross(v, ln2[0]-ln1[0])/cross(v, u))

# 入力:３点座標、リターン:外接円の円心座標、半径を表すリスト
def circumscribed_circle(p1, p2, p3):
	p12 = (p1+p2)/2
	p23 = (p2+p3)/2
	ln1 = [p12, p12+(p1-p2)*complex(0, 1)]
	ln2 = [p23, p23+(p2-p3)*complex(0, 1)]
	c = crossPointLL(ln1, ln2)
	return [c, dist(c, p1)]

for i in range(int(input())):
	p = list(map(float, input().split()))
	p1 = complex(p[0], p[1])
	p2 = complex(p[2], p[3])
	p3 = complex(p[4], p[5])
	ans = circumscribed_circle(p1, p2, p3)
	print(format(ans[0].real+EPS, ".3f"), format(ans[0].imag+EPS, ".3f"), format(ans[1]+EPS, ".3f"))

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 xp-t*yp,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: def main():
	import math
	n = int(input())
	w = [0]*6

	for _ in range(n):
		x1, y1, x2, y2, x3, y3 = map(float, input().split())
		w[0] = 2*(x2-x1)
		w[1] = 2*(y2-y1)
		w[2] = x2**2 + y2**2 - x1**2 - y1**2
		w[3] = 2*(x3-x1)
		w[4] = 2*(y3-y1)
		w[5] = x3**2 + y3**2 - x1**2 - y1**2

		x, y = solve(w)

		r = math.sqrt((x-x1)**2 + (y-y1)**2)

		print("{:.3f} {:.3f} {:.3f}".format(x, y, r))


def solve(w):
	x = (w[2]*w[4]-w[1]*w[5]) / (w[0]*w[4]-w[1]*w[3])
	y = (w[2]*w[3]-w[0]*w[5]) / (w[1]*w[3]-w[0]*w[4])
	x = round(x, 3)
	y = round(y, 3)
	if x == -0.0:
	    x = 0.0
	if y == -0.0:
	    y = 0.0
	return x, y


if __name__ == '__main__':
	main()

Python: import math

def solve(a,b,c,d,e,f):
	x = - (d*(f**2+e**2-b**2-a**2) + b*(-f**2-e**2) + b**2*f + a**2*f + d**2*(b-f) + c**2*(b-f)) / (c*(2*f-2*b) - 2*a*f + 2*b*e + d*(2*a-2*e))
	y = (c*(f**2+e**2-b**2-a**2) + a*(-f**2-e**2) + b**2*e + a**2*e + d**2*(a-e) + c**2*(a-e)) / (c*(2*f-2*b) - 2*a*f + 2*b*e + d*(2*a - 2*e))
	r = math.hypot(x-a, y-b) 
	return x,y,r

n = int(input())
for _ in range(n):
	a,b,c,d,e,f = map(float, input().split())
	x,y,r = solve(a,b,c,d,e,f)
	print("{:.3f} {:.3f} {:.3f}".format(x, y, r))