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asinh(3)
NAME
  asinh, acosh, atanh - Compute inverse hyperbolic functions

LIBRARY
  Math Library (libm.a)

SYNOPSIS
  #include <math.h>

  double asinh	(double x);
  float	 asinhf (float	x);
  double acosh	(double x);
  float	 acoshf (float	x);
  double atanh	(double x);
  float	 atanhf (float	x);

STANDARDS
  Interfaces documented on this reference page conform to industry standards
  as follows:

  asinh():  XPG4-UNIX

  acosh():  XPG4-UNIX

  atanh():  XPG4-UNIX

  Refer to the standards(5) reference page for more information about
  industry standards and associated tags.

DESCRIPTION
  The asinh() and asinhf() functions return the hyperbolic arc sine of x, in
  the range [-infinity, +infinity] where asinh(x) = ln(x + sqrt(x**2 + 1)).
  The asinh() function is the reverse function of sinh() where asinh(sinh(x))
  = x.

  The acosh()  and acoshf() functions return the hyperbolic arc cosine of x,
  in the range [1, +infinity] where acosh(x) = ln(x + sqrt(x**2 - 1)).	The
  acosh() function is the reverse function of cosh() where acosh(cosh(x)) =
  x.

  The atanh() and atanhf() functions return the hyperbolic arc tangent of x,
  in the range (-1, 1). The atanh() function is the reverse function of
  tanh() where atanh(tanh(x)) = x.

  The following table describes function behavior in response to exceptional
  arguments:








  __________________________________________________
  Function   Exceptional Argument   Routine Behavior
  __________________________________________________
  asinh()    None		    N/A
  asinhf()   None		    N/A
  acosh()    x<1		    Invalid argument
  acoshf()   x<1		    Invalid argument
  atanh()    x>1 or x=1		    Invalid argument
  atanhf()   x>1 or x=1		    Invalid argument
  __________________________________________________