atan

asin

#include <cmath>float asin(float arg);double asin(double arg);  long double asin(long double arg); 

The asin( ) function returns the arc sine of arg. The argument to asin( ) 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( ).