Calculates the hyperbolic arc tangent of a floating-point number.

[Format]

#include <math.h>

double atanh(double d);

float atanhf(float d);

long double atanhl(long double d);

[Parameters]

d Floating-point number for which hyperbolic arc tangent is to be computed

[Return values]

Normal: Hyperbolic arc tangent of d

Abnormal: Domain error: Returns HUGE_VAL, HUGE_VALF, or HUGE_VALL depending on the function.

Range error: Returns not-a-number.

[Remarks]

A domain error occurs for a value of d not in the range [–1, +1]. A range error may occur for a value of d equal to –1 or 1.