GNU Scientific Library – Reference Manual: Mathematical Constants

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### 4.1 Mathematical Constants

The library ensures that the standard BSD mathematical constants are defined. For reference, here is a list of the constants:

`M_E`

  The base of exponentials, e

`M_LOG2E`

  The base-2 logarithm of e, \log_2 (e)

`M_LOG10E`

  The base-10 logarithm of e, \log_10 (e)

`M_SQRT2`

  The square root of two, \sqrt 2

`M_SQRT1_2`

  The square root of one-half, \sqrt{1/2}

`M_SQRT3`

  The square root of three, \sqrt 3

`M_PI`

  The constant pi, \pi

`M_PI_2`

  Pi divided by two, \pi/2

`M_PI_4`

  Pi divided by four, \pi/4

`M_SQRTPI`

  The square root of pi, \sqrt\pi

`M_2_SQRTPI`

  Two divided by the square root of pi, 2/\sqrt\pi

`M_1_PI`

  The reciprocal of pi, 1/\pi

`M_2_PI`

  Twice the reciprocal of pi, 2/\pi

`M_LN10`

  The natural logarithm of ten, \ln(10)

`M_LN2`

  The natural logarithm of two, \ln(2)

`M_LNPI`

  The natural logarithm of pi, \ln(\pi)

`M_EULER`

  Euler’s constant, \gamma