Legacy Document

tan

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

double_t tan (double_t x);

x

Any finite floating-point number.

DESCRIPTION

The tan function returns the tangent of its argument. The argument is the measure of an angle expressed in radians. This function is antisymmetric.

The atan function performs the inverse operation $(arctan(y))$ .

EXCEPTIONS

When x is finite and nonzero, the result of $tan(x)$ might raise one of the following exceptions:

• inexact (for all finite, nonzero values of x)
• underflow (if the result is inexact and must be represented as a denormalized number or 0)

SPECIAL CASES

Table 10-22 shows the results when the argument to the tan function is a zero, a NaN, or an Infinity, plus other special cases for the tan function.

Special cases for the tan function

Operation	Result	Exceptions raised
$tan(pi)$	0	Inexact
$tan(pi/2)$	+	Inexact
$tan(+0)$	+0	None
$tan(-0)$	$-0$	None
$tan(NaN)$	NaN	None[43]
$tan(+$ )	NaN	Invalid
$tan(-$ )	NaN	Invalid

EXAMPLES

z = tan(pi);   /* z = 0. The inexact exception is raised. */
z = tan(pi/2); /* z = +INFINITY. The inexact exception is 
                  raised. */
z = tan(pi/4); /* z = 1. The inexact exception is raised. */

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