View Compilation Error

0_0_32442482_4271.cpp: In function 'bool judge(int, int, int, int)':
0_0_32442482_4271.cpp:5:12: error: 'M_PI' was not declared in this scope
 #define PI M_PI
            ^
0_0_32442482_4271.cpp:15:26: note: in expansion of macro 'PI'
     for(double a=0.f; a<=PI/2.f; a+=0.1){
                          ^