atan

compute the arctangent

Synopsis:

#include <math.h>
double atan( double x );

Description:

The atan() function computes the principal value of the arctangent of x.

Returns:

the arctangent in the range (-PI/2, PI/2).

See also:

acos(), asin(), atan2()

Examples:

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

void main()
  {
    printf( "%f\n", atan(.5) );
  }

produces the output:

0.463648

Classification:

ANSI

Systems:

Math