WIN32 isn’t the correct macro. It’s actually _WIN32. Either way, that’s a macro defined by Visual Studio C++, but you’re using MinGW so the actual macro to check for is __MINGW32__ or (64). This still is the wrong way to do things, since MSDN requires:
#define _USE_MATH_DEFINES // for C++
#include <cmath>
In order to access the math constants. MinGW already does this.
solved Defined macro not recognized