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atanh, atanhf, atanhl


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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  


Floating-point 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.

InputSEH ExceptionMatherr Exception
± QNAN,INDnonenone
X ≥ 1; x ≤ -1nonenone

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.

FunctionC headerC++ header
atanh, atanhf, atanhl<math.h><cmath>

For additional compatibility information, see Compatibility.

// 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  

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

Floating-Point Support
Long Double
acos, acosf, acosl
asin, asinf, asinl
atan, atanf, atanl, atan2, atan2f, atan2l
cos, cosf, cosl, cosh, coshf, coshl
sin, sinf, sinl, sinh, sinhf, sinhl
tan, tanf, tanl, tanh, tanhf, tanhl