Arc tangent

[Classification]

Mathematical library

[Syntax]

#include <math.h>

long double __far atanl(long double x); (C99)

[Return value]

Returns the arc tangent (arctangent) of x. The returned value is in radian and in a range of [-π / 2, π / 2].

When x is Not-a-Number, this function returns Not-a-Number and sets macro EDOM to global variable errno.

When x is -0, this function returns -0.

If the solution is a denormal number, atanl sets macro ERANGE to global variable errno.

[Description]

This function calculates the arc tangent (arctangent) of x.