Arc tangent

[Classification]

Mathematical library

[Syntax]

#include <math.h>

double atan(double x);

[Return value]

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

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

[Description]

This function calculates the arc tangent (arctangent) of x. Specify x as, -1 <= x <= 1.