View Compilation Error

0_0_30453144_31841.cpp: In function 'double jd(int, int)':
0_0_30453144_31841.cpp:18:21: error: 'M_PI' was not declared in this scope
   return 180-re*180/M_PI;
                     ^
0_0_30453144_31841.cpp:19:16: error: 'M_PI' was not declared in this scope
  return re*180/M_PI;
                ^