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Function: float llAcos( float val );

Returns a float that is the arccosine in radians of val

• float val must fall in the range [-1.0, 1.0]

The returned value is in the range [0.0, PI][1], or NaN signifying a complex result when the parameter is out of range.


  • Triggers a Math Error for complex results if not compiled in Mono.
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//  This example exercises the full valid range of argument from -1.0 to +1.0

    touch_start(integer num_detected)
        float random = llFrand(2.0) - 1.0;

        llOwnerSay("The arccosine of " + (string)random + " is " + (string)llAcos(random));
//An example for the Law of Cosines to calculate any angle of a triangle from 3 known side lengths.

    touch_start(integer num_detected)
        vector t=< llFrand(9.0)+1.0 , llFrand(9.0)+1.0 , llFrand(9.0)+1.0 >; //the 3 values of this vector are used to set the lengths of 3 sides of a triangle.

        float anglexy=llAcos( (t.x*t.x+t.y*t.y-(t.z*t.z)) / ( 2*t.x*t.y) ) //Law Of Cosines

        llOwnerSay("Using the Law Of Cosines, the angle of a triangle between side a="+(string)t.x+"and side b="+(string)t.y+"is = "+(string)anglexy+" radians="+(string)(anglexy*RAD_TO_DEG)+"° and that angle is not on side c="+(string)t.z);

See Also


• llSin llAsin sine & inverse Sine
• llCos cosine
• llTan llAtan2 tangent & inverse tangent


•  "Wikipedia logo"Inverse trigonometric function

Deep Notes

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


function float llAcos( float val );