4 number Rotation to 3 number conversion

Please forgive this newbie question.
I need rotation numbers in the 3 number vector notation for a configuration notecard.
The prim-sitter script is giving me a 4-number rotation.
How do I convert this?
The affected script is no mod so I can't do anything there.
Thank you .. if this is too basic I would appreciate being pointed to the right source.

llRot2Euler

Thanks Ralph ... much appreciated .. not much fun being ignored ..lol!!

You probably also want to convert from Radians to Degrees...

vector rotationInDegrees = llRot2Euler(theRotation) * RAD_TO_DEG;

and reversed:

rotation theRotation = llEuler2Rot(rotationInDegrees * DEG_TO_RAD);