View Compilation Error

0_0_37795476_14103.cpp: In function 'bool Onsegment(Point, Point, Point)':
0_0_37795476_14103.cpp:76:23: error: 'p' was not declared in this scope
  return dcmp(Cross(a1-p,a2-p))==0&&dcmp(Dot(a1-p,a2-p))<0;
                       ^
0_0_37795476_14103.cpp: In function 'double PolygonArea(Point*, int)':
0_0_37795476_14103.cpp:82:3: error: 'area' was not declared in this scope
   area+=Cross(p[i]-p[0],p[i+1]-p[0]);
   ^
0_0_37795476_14103.cpp:83:9: error: 'area' was not declared in this scope
  return area/2;
         ^
0_0_37795476_14103.cpp: In function 'void solve(Vector, Vector, double)':
0_0_37795476_14103.cpp:98:12: error: 'pi' was not declared in this scope
  double t2=pi/2-t1;
            ^