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Function: float llAtan2( float y, float x );

Returns a float that is the "Wikipedia logo"arctangent2 of y, x.

• float y
• float x

Similar to the "Wikipedia logo"arctangent(y/x) except it utilizes the signs of x & y to determine the quadrant and avoids division by zero.


If x is positive zero and...

  • y is zero, zero is returned.
  • y is positive, PI/2 is returned.
  • y is negative, -PI/2 is returned.

If x is negative zero and...

  • y is positive zero, PI is returned.
  • y is negative zero, -PI is returned.
  • y is positive, PI/2 is returned.
  • y is negative, -PI/2 is returned.


if((string)x != (string)0.0 && y == 0.0)//negative zero
    return PI * ~-2*((string)y != (string)0.0));
return ((y > 0) - (y < 0)) * PI_BY_TWO;

The returned value is in the range [-PI, PI][1].


    float num1 = llFrand(100.0);
    float num2 = llFrand(100.0);

    llOwnerSay("y = " + (string)num1);
    llOwnerSay("x = " + (string)num2);

    llOwnerSay("The arctangent of y divided by x is " + (string)llAtan2(num1, num2));
//Function with input of a vector determining the position of a target and returning
//a string with the literal compass-direction of that target towards your position
//by Ramana Sweetwater 2009/01, any use allowed license :-)
//corrected by Patrick Muggins

string compass (vector target) 
    vector source = llGetPos();
    list DIRS =["W","NW","N","NE","E","SE","S","SW","W"];
    integer index = llCeil(3.5 - (4 * llAtan2(target.y - source.y, target.x - source.x) / PI));
    return llList2String(DIRS, index);
/Compass QA

See Also


• llSin llAsin sine & inverse Sine
• llCos llAcos cosine & inverse cosine
• llTan tangent


•  "Wikipedia logo"Atan2
•  "Wikipedia logo"Inverse trigonometric function

Deep Notes

Search JIRA for related Issues


  1. ^ The ranges in this article are written in Interval Notation.


function float llAtan2( float y, float x );


An analog clock
passes through infinity
twice every single hour