URAL1075[A thread in a space]

数学题。


CODE:


/*


PROGRAM: $PROGRAM


AUTHOR: Su Jiao


DATE: 2010-4-9


DESCRIPTION:


$DESCRIPTION


*/


#include <iostream>


using std::cin;


using std::cout;


#include <fstream>


using std::ifstream;


using std::ofstream;


#include <sstream>


using std::stringstream;


using std::endl;


#include <vector>


using std::vector;


#include <string>


using std::string;


#include <stack>


using std::stack;


#include <queue>


using std::queue;


using std::priority_queue;


#include <set>


using std::set;


#include <map>


using std::map;


using std::pair;


using std::make_pair;


#include <algorithm>


using std::sort;


#include <iomanip>


#include <cassert>


//using std::assert;


#include <cmath>


using std::sqrt;


using std::acos;


 


struct Point{double x,y,z;};


double d(const Point& A,const Point& B)


{


       return sqrt((A.x-B.x)*(A.x-B.x)


                  +(A.y-B.y)*(A.y-B.y)


                  +(A.z-B.z)*(A.z-B.z));


}


double s(double a,double b,double c)


{


       double p=(a+b+c)/2;


       return sqrt(p*(p-a)*(p-b)*(p-c));


}


 


class Application


{


      Point A,B,C;


      double R;


      public:


      Application()


      {


                   cin>>A.x>>A.y>>A.z


                      >>B.x>>B.y>>B.z


                      >>C.x>>C.y>>C.z


                      >>R;


      }


      int run()


      {


          double AB=d(A,B);


          double AC=d(A,C);


          double BC=d(B,C);


         


          cout<<std::setiosflags(std::ios::fixed)<<std::setprecision(2);


          if (acos((AC*AC+BC*BC-AB*AB)/(2*AC*BC))-acos(R/AC)-acos(R/BC)<0)


             cout<<AB<<endl;


          else


          {


              double answer=0;


              answer=


              sqrt(AC*AC-R*R)


              +sqrt(BC*BC-R*R)


              +R*(acos((AC*AC+BC*BC-AB*AB)/(2*AC*BC))-acos(R/AC)-acos(R/BC));


              cout<<answer<<endl;


          }


          return 0;


      }


};


 


int main()


{


    Application app;


    return app.run();


}