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arc tangent function of one variable

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NAME

atan

INTERFACE

#include <math.h> double atan ( double x ) long atanl ( long double x ) float atanf ( float x )

DESCRIPTION

The atan function computes the principal value of the arc tangent of x, returning a value in the range $[-\pi/2, + \pi/2]$

The arc tangent is often also donated as $tan^{-1}(x)$ . This is a multi-valued function of the following form:

Example 1

#include <stdio.h>
#include <math.h>

int main(void)
{
  double result, x=0.5;
  result = atan(x);
  printf("The arc tan of %lf is %lf\n", x, result);
}

output

The arc tan of 0.500000 is 0.463648

SPECIAL VALUES

atan ( ±0 ) returns ±0. atan ( ±∞ ) returns ±pi/2

STANDARDS

The atan function conforms to ISO/IEC 9899:1999(E).