atanh, atanhf, atanhl

Article
06/05/2017

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Calculates the inverse hyperbolic tangent.

Syntax

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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