Language: C++

//ツ三ツ角ツ形ツづ個外ツ静堋円ツづ個陳?心ツづ? ツ三ツ角ツ形ツづ個静シツ閉ェツづ個青つ陳シツ禿アツ督卍閉ェツ静シツつェツ古ーツづュツづゥツ湘ェツ渉環づ可づ按づゥ.
//ツつアツづ個づヲツつ、ツづ按甘エツ可スツ学ツ的ツづ按姪「ツ妥ィツづーツ嘉ーツつュツづ?つォツづ? ツ暗按可コツづ個ペ-ツジツづ個δ可イツブツδ可δ環づーツ参ツ考ツづ可つキツづゥツづ?嘉ーツつォツづ「ツつキツつ「.
// - http://www.deqnotes.net/acmicpc/2d_geometry/
// - http://www.prefield.com/algorithm/index.html

#include <iostream>
#include <complex>
#include <vector>
using namespace std;

typedef complex<double> P;

P p[3]; //ツ三ツ角ツ形ツづ個三ツ点

//ツ外ツ静?
double cross(const P &a, const P &b){
  return imag(conj(a) * b);
}

//ツ静シツ閉ェ/ツ陳シツ静シツ用ツづ個型
struct L : public vector<P> {
  L(const P &a, const P &b){
    push_back(a);
    push_back(b);
  }
};

//ツ陳シツ静シ2ツづつづ個古ーツ点ツづーツ仰?づ淞づゥ
P crosspoint(const L &l, const L &m){
  double A = cross(l[1] - l[0], m[1] - m[0]);
  double B = cross(l[1] - l[0], l[1] - m[0]);
  return m[0] + B / A * (m[1] - m[0]);
}

//ツ静シツ閉ェabツづ個青つ陳シツ禿アツ督卍閉ェツ静シツづーツ仰?づ淞づゥ
L getBisection(const P &a, const P &b){
  P s = (a + b) / 2.0; //ツ陳?点
  P t = (b - a) * P(0, 1); //ツ静シツ閉ェabツづ個法ツ静シツベツクツトツδ仰づーツ偲ヲツ督セ

  //ツ静シツ閉ェabツづ個青つ陳シツ禿アツ督卍閉ェツ静シツづ? ツ点sツつゥツづァs+tツづ鳴伸ツづ堕づゥツ陳シツ静シ
  return L(s, s + t);
}

void solve(){
  //ツ三ツ角ツ形ツづ個静シツ閉ェツづ個青つ陳シツ禿アツ督卍閉ェツ静シツづー2ツづつ偲ヲツ督セツつキツづゥ
  L l1 = getBisection(p[0], p[1]);
  L l2 = getBisection(p[1], p[2]);

  //ツ外ツ静堋円ツづ個陳?心ツづ? l1ツづ?2ツつェツ古ーツ債キツつオツつスツ点
  P o = crosspoint(l1, l2);

  //ツ三ツ角ツ形ツづ個任ツ暗督づ個陳クツ点ツつゥツづァ, ツ陳?心ツづ慊づ?づ個仰猟猟」ツづーツ偲ヲツづェツづ? ツ板シツ径ツづ可づ按づゥ
  printf("%.3f %.3f %.3f\n", o.real(), o.imag(), abs(o - p[0]));
}

int main(){
  int n;
  cin >> n;

  for(int i = 0; i < n; i++){
    for(int j = 0; j < 3; j++){
      cin >> p[j].real() >> p[j].imag();
    }

    solve();
  }
}

Compiler output:
a.cc: In function 'int main()':
a.cc:62:11: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'double')
   62 |       cin >> p[j].real() >> p[j].imag();
      |       ~~~ ^~ ~~~~~~~~~~~
      |       |               |
      |       |               double
      |       std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/iostream:42,
                 from a.cc:6:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:181:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  181 |       operator>>(int& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:181:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'double&' to an rvalue of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:62:23: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'double'
   62 |       cin >> p[j].real() >> p[j].imag();
      |              ~~~~~~~~~^~
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:25: note:   no known conversion for argument 1 from 'double' to 'void*&'
  328 |       operator>>(void*& __p)
      |                  ~~~~~~~^~~
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:36: note:   no known conversion for argument 1 from 'double' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |                  ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]'
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:32: note:   no known conversion for argument 1 from 'double' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |                  ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~
/usr/include/c++/14/istream:133:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]'
  133 |       operator>>(ios_base& (*__pf)(ios_base&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:133:30: note: