M_PI flagged as undeclared identifier

Question

When I compile the code below, I got these error messages:

(Error  1   error C2065: \'M_PI\' : undeclared identifier 
2   IntelliSense: identifier \"M_PI\"          


        

Answer 1

It sounds like you're using MS stuff, according to their docs

Math Constants are not defined in Standard C/C++. To use them, you must first define _USE_MATH_DEFINES and then include cmath or math.h.

So you need something like

#define _USE_MATH_DEFINES
#include 

as a header.