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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>

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