ASIN(3) Library Functions Manual ASIN(3)

asin — arc sine function

#include <math.h>

double asin(double x);

The asin() function computes the principal value of the arc sine of x. The value of x should be in the range [-1,1].

An application wishing to check for error situations should set errno to 0, then call asin(). If errno is non-zero on return, or the return value is NaN, an error has occurred.

Upon successful completion, asin() returns the arc sine of x , in the range [- /2, /2] radians. If the value of x is not in the range [-1,1], and is not ±Inf or NaN, either 0.0 or NaN is returned and errno is set to [EDOM].

If x is NaN, NaN is returned and errno may be set to [EDOM].

If x is ±Inf, either 0.0 is returned and errno is set to [EDOM] or NaN is returned and errno may be set to [EDOM].

If the result underflows, 0.0 is returned and errno may be set to [ERANGE].

The asin() function will fail if:

The value x is not ±Inf or NaN and is not in the range [-1,1].

The asin() function may fail if:

The value of x is ±Inf or NaN.
The result underflows.

No other errors will occur.

None.

None.

None.

isnan(3) , sin(3) , <math.h> .

Derived from Issue 1 of the SVID.

February 1997 posix.fail