asin, asinf : arc sine

Synopsis

#include <math.h>
double asin(double x);
float asinf(float x);
```### Description

asin computes the inverse sine (arc sine) of the argument x. Arguments to asin must be in the range -1 to 1. asinf is identical to asin, other than taking and returning floats. You can modify error handling for these routines using matherr.### Returns

If x is not in the range -1 to 1, asin and asinf return NaN (not a number), set the global variable errno to EDOM, and issue a DOMAIN error message. You can change this error treatment using matherr.

---

**Authoritative source**: BUSMASTER DITA help source `asin.dita`, compiled into `BUSMASTER.CHM` with the application.