LSL Wiki : llAcos

float llAcos(float val)

Returns the arccosine or inverse cosine in radians of val.

Basically, it is the inverse of cosine (llCos), just as as division is the inverse of multiplication.

Example:

float cosine_return;
float arccosine_return;

cosine_return = llCos( 1 );
arccosine_return = llAcos( cosine_return );

llOwnerSay( "cosine_return = llCos( 1 ) == " + (string)cosine_return );
llOwnerSay( "arccosine_return = llACos( cosine_return ) == " + (string)arccosine_return );

This would result in the following:

cosine_return = llCos( 1 ) == 0.540302
arccosine_return = llACos( cosine_return ) == 1.000000

Compare with llCos.

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Functions | Math