@Ravi: i have rarely seen triangular plots. Yes, there is something called "Gaumukh" which is like the cow's mouth - narrow from the entrance and wider as you move forward. They arent equally considered in Vastu. Whether a Gaumukha or a circular plot is not advisable since the energies are obstructed and do not have a proper place to move out. Consider the case of a local bus where just one door is there - you would not be able to sit comfortably in it coz there will be a stressed entrance for all the people trying to barge in or move out.