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Math Constants

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

#define _USE_MATH_DEFINES // for C
#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

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.

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