atan

INTERFACE

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

#include <complex.h>
complex atan(complex x)
double complex catan(double complex x)
float complex catanf(float complex x)
long double complex catanl(long double complex x)

DESCRIPTION

The atan function computes the principal value of the arc tangent of x, returning a value in the range . The arc tangent is also often denoted as .

The complex inverse tangent is defined by:

(1)

#include <stdio.h>
#include <math.h>
int main(void)
{
  double result, x = 0.6325;
  result = atan(x);
  printf("The arc sin of %lf is %lf\n", x, result);
}

SPECIAL VALUES

atan ( ±0 ) returns ±0.

atan ( ±∞ ) returns ±.

SEE ALSO

acos, asin, atan2, cos, cosh, sin, sinh, tan, tanh

STANDARDS

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

COMPATIBILITY