standard.C.math.atan

atan is available since version 1.0.

Prototype:

number atan(number tangent)

Parameters

tangent
[in] Value whose arctangent is to be calculated

Description:

Returns the arctangent of tangent in the range of -M_PI/2 to M_PI/2 radians.
If tangent is 0, atan returns 0.

Return value:

Returns the arctangent of tangent in the range of -M_PI/2 to M_PI/2 radians. If tangent is 0, atan returns 0.

Example
import standard.C.math

class Main {
     function Main() {
          var angle;
          var radians;
          var result;

          // Calculate the tangent of 30 degrees.
          angle = 30;
          radians = angle * M_PI/180;
          result = tan(radians);
          echo "The tangent of 30 degrees is " + result + ".\n";

          // Calculate the arctangent of the previous tangent.
          radians = atan(result);
          angle = radians * 180/M_PI;
          echo "The previous tangent is equivalent to " + ceil(angle) + " degrees.\n"; 
     }
} 
 

Results 
The tangent of 30 degrees is 0.57735026918962573.
The previous tangent is equivalent to 30 degrees.