View Compilation Error

0_0_20041090_18427.cpp: In member function 'void poly::FFT(int, int)':
0_0_20041090_18427.cpp:35:20: error: 'M_PI' was not declared in this scope
    cop step={cos(2*M_PI*type/h),sin(2*M_PI*type/h)};
                    ^