Legacy Document

tanh

You can use the tanh function to compute the hyperbolic tangent of a real number.

double_t tanh (double_t x);

x

Any floating-point number.

DESCRIPTION

The tanh function returns the hyperbolic tangent of its argument. The return value is in the range [-1, +1]. This function is antisymmetric.

The atanh function performs the inverse operation $(arctanh(y))$ .

EXCEPTIONS

When x is finite and nonzero, the result of $tanh(x)$ raises the following exception:

• inexact (for all finite, nonzero values of x)

SPECIAL CASES

Table 10-29 shows the results when the argument to the tanh function is a zero, a NaN, or an Infinity.

Special cases for the tanh function

Operation	Result	Exceptions raised
$tanh(+0)$	+0	None
$tanh(-0)$	$-0$	None
$tanh(NaN)$	NaN	None[51]
$tanh(+$ )	+1	None
$tanh(-$ )	-1	None

EXAMPLES

z = tanh(1.0);    /* z  0.761594. The inexact exception is 
                     raised. */
z = tanh(-1.0);   /* z  0.761594. The inexact exception is 
                     raised. */

---

[51] If the NaN is a signaling NaN, the invalid exception is raised.