Calculates the arc tangent of a floating-point number.

[Format]

#include <math.h>

double atan (double d);

float atanf (float d);

long double atanl (long double d);

[Parameters]

d Floating-point number for which arc tangent is to be computed

[Return values]

Arc tangent of d

[Remarks]

The atan function returns the arc tangent in the range (–π/2, +π/2) by the radian.

If the function call is replaced by code that uses a trigonometric function unit, the function might no longer be reentrant. For details, refer to the item about -tfu in the section on compile options.