View Compilation Error

0_0_33525974_28402.cpp: In function 'double PA(Point*, int)':
0_0_33525974_28402.cpp:41:45: error: 'Cross' was not declared in this scope
         area += Cross(p[i]-p[0], p[i+1]-p[0]);
                                             ^
0_0_33525974_28402.cpp: In function 'int main()':
0_0_33525974_28402.cpp:87:37: error: 'Angle' was not declared in this scope
             double an = Angle(v1, v2)/2;
                                     ^
0_0_33525974_28402.cpp:88:40: error: 'ang' was not declared in this scope
             double len = (double)r/sin(ang);
                                        ^
0_0_33525974_28402.cpp:89:39: error: 'Rotate' was not declared in this scope
             Vector v3 = Rotate(v1, ang);
                                       ^
0_0_33525974_28402.cpp:90:40: error: 'Length' was not declared in this scope
             Point o = p[1]+v3/Length(v3)*len;
                                        ^