It is a homework question (never been a fan of chemistry!).  I am studying aromatherapy and have been asked to draw the carbon skeleton of an isoprene unit, which I have done.  I am then asked to draw two isoprene units to form an acyclic chain as well as a cyclic chain and then a sesquiterpene and so on.  What I want to know is, what are the rules of joining isoprene units?  Am I supposed to know how they are drawn by the information given? Is there a pattern?