math-constants.md

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Learn more about: Math Constants	Math Constants	11/04/2016	c.constants.math _USE_MATH_DEFINES CORECRT_MATH_DEFINES/M_E CORECRT_MATH_DEFINES/M_LOG2E CORECRT_MATH_DEFINES/M_LOG10E CORECRT_MATH_DEFINES/M_LN2 CORECRT_MATH_DEFINES/M_LN10 CORECRT_MATH_DEFINES/M_PI CORECRT_MATH_DEFINES/M_PI_2 CORECRT_MATH_DEFINES/M_PI_4 CORECRT_MATH_DEFINES/M_1_PI CORECRT_MATH_DEFINES/M_2_PI CORECRT_MATH_DEFINES/M_2_SQRTPI CORECRT_MATH_DEFINES/M_SQRT2 CORECRT_MATH_DEFINES/M_SQRT1_2 M_E M_LOG2E M_LOG10E M_LN2 M_LN10 M_PI M_PI_2 M_PI_4 M_1_PI M_2_PI M_2_SQRTPI M_SQRT2 M_SQRT1_2	M_PI constant M_PI_2 constant math constants M_2_PI constant M_1_PI constant M_E constant USE_MATH_DEFINES constant M_LOG2E constant M_LOG10E constant M_LN10 constant M_SQRT1_2 constant _USE_MATH_DEFINES constant M_PI_4 constant constants, math M_2_SQRTPI constant M_SQRT2 constant M_LN2 constant	db533c3f-6ae8-4520-9d35-c8fabbef3529

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