Math Constants
#include <math.h>
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" are not defined in Standard C/C++. Therefore, in order to use them, you have to first define _USE_MATH_DEFINES and then include cmath or math.h as below.
If compiling as C++:
#define _USE_MATH_DEFINES
#include <cmath>
If compiling as C:
#define _USE_MATH_DEFINES
#include <math.h>
