Math constants

Microsoft provides several predefined preprocessor macros for common math constants.

Syntax

#define _USE_MATH_DEFINES // for C++
#include <cmath>

#define _USE_MATH_DEFINES // for C
#include <math.h>

Remarks

The following symbols are defined for the values of their indicated expressions:

Symbol	Expression	Value
M_E	e	2.71828182845904523536
M_LOG2E	log2(e)	1.44269504088896340736
M_LOG10E	log10(e)	0.434294481903251827651
M_LN2	ln(2)	0.693147180559945309417
M_LN10	ln(10)	2.30258509299404568402
M_PI	pi	3.14159265358979323846
M_PI_2	pi/2	1.57079632679489661923
M_PI_4	pi/4	0.785398163397448309616
M_1_PI	1/pi	0.318309886183790671538
M_2_PI	2/pi	0.636619772367581343076
M_2_SQRTPI	2/sqrt(pi)	1.12837916709551257390
M_SQRT2	sqrt(2)	1.41421356237309504880
M_SQRT1_2	1/sqrt(2)	0.707106781186547524401

The math constants aren't defined in Standard C/C++. To use them, you must first define _USE_MATH_DEFINES, and then include <cmath> or <math.h>.

The file <ATLComTime.h> includes <math.h> when your project is built in Release mode. If you use one or more of the math constants in a project that also includes <ATLComTime.h>, you must define _USE_MATH_DEFINES before you include <ATLComTime.h>.

See also

Global constants