Legacy Document

asin

You can use the asin function to compute the arc sine of a real number between -1 and 1.

double_t asin (double_t x);

x

Any floating-point number in the range -1 x 1.

DESCRIPTION

The asin function returns the arc sine of its argument. The return value is expressed in radians in the range [ $-pi/2$ , + $pi/2$ ]. This function is antisymmetric.

 such that  for -1  x  1

The sin function performs the inverse operation $(sin(y))$ .

EXCEPTIONS

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

• inexact (for all finite, nonzero values of x)
• invalid (if |x| > 1)
• underflow (if the result is inexact and must be represented as a denormalized number or 0)

SPECIAL CASES

Table 10-24 shows the results when the argument to the asin function is a zero, a NaN, or an Infinity, plus other special cases for the asin function.

Special cases for the asin function

Operation	Result	Exceptions raised
$asin(x)$ for |x| > 1	NaN	Invalid
$asin(-1)$	-\x86/2	Inexact
$asin(+1)$	\x86/2	Inexact
$asin(+0)$	+0	None
$asin(-0)$	$-0$	None
$asin(NaN)$	NaN	None[45]
$asin(+$ )	NaN	Invalid
$asin(-$ )	NaN	Invalid

EXAMPLES

z = asin(1.0);    /* z = arcsin 1 = \x86/2. The inexact exception is 
                     raised. */
z = asin(-1.0);   /* z = arcsin -1 = -\x86/2. The inexact exception 
                     is raised. */

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