atan, atanf : arc tangent

Synopsis

#include <math.h>
double atan(double x);
float atanf(float x);
```### Description

atan computes the inverse tangent (arc tangent) of the input value. atanf is identical to atan, save that it operates on floats.### Returns

atan and atanf return the calculated value

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**Authoritative source**: BUSMASTER DITA help source `atan.dita`, compiled into `BUSMASTER.CHM` with the application.