atanh, atanhf, atanhl

Article
04/28/2015

Calculates the inverse hyperbolic tangent.

double atanh(
   double x 
);
float atanh(
   float x 
);  // C++ only
long double atanh(
   long double x
);  // C++ only
float atanhf(
   float x 
);
long double atanhl(
   long double x
);

Parameters

x
Floating-point value.

Return Value

The atanh functions return the inverse hyberbolic tangent (arc hyperbolic tangent) of x. If x is greater than 1, or less than –1, errno is set to EDOM and the result is a quiet NaN. If x is equal to 1 or -1, a positive or negative infinity is returned, respectively, and errno is set to ERANGE.

Input	SEH Exception	Matherr Exception
± QNAN,IND	none	none
X ≥ 1; x ≤ -1	none	none

Remarks

Because C++ allows overloading, you can call overloads of atanh that take and return float or long double values. In a C program, atanh always takes and returns double.

Requirements

Function	C header	C++ header
atanh, atanhf, atanhl	<math.h>	<cmath>

For additional compatibility information, see Compatibility.

Example

// crt_atanh.c
// This program displays the hyperbolic tangent of pi / 4
// and the arc hyperbolic tangent of the result.
//

#include <math.h>
#include <stdio.h>

int main( void )
{
   double pi = 3.1415926535;
   double x, y;

   x = tanh( pi / 4 );
   y = atanh( x );
   printf( "tanh( %f ) = %f\n", pi/4, x );
   printf( "atanh( %f ) = %f\n", x, y );
}

tanh( 0.785398 ) = 0.655794
atanh( 0.655794 ) = 0.785398

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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