Math Constants
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The latest version of this topic can be found at 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 |
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.
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.