Tóm Tắt
Math Constants
In this article
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
.
See also
Global Constants