asin

#include <math.h>float asinf(float arg);double asin(double arg); 
long double asinl(long double arg);

asinf( ) and asinl( ) were added by C99.

The asin( ) family of functions returns the arc sine of arg. The argument must be in the range –1 to 1; otherwise, a domain error will occur.

Related functions are acos( ), atan( ), atan2( ), sin( ), cos( ), tan( ), sinh( ), cosh( ), and tanh( ).