View Compilation Error

0_0_39818224_9613.cpp: In function 'double calc_angle(int, int, int)':
0_0_39818224_9613.cpp:10:43: error: 'M_PI' was not declared in this scope
   10 |     return atan2(h, abs(x - q)) * 180.0 / M_PI;
      |                                           ^~~~