Projection of Apex of Right Pyramid
Definition of a right Pyramid : The slant height of all edges are equal.
This demonstration would like to show that the projection of Apex of a right Pyramid would be coincided with the circumcentre of the base of the pyramid.
1.  Ask students how to find the projection (V') of the Apex (V) of the 
     pyramid. ( After discussion, please tick "projection" to show it.)
2.  Ask students which centres of triangle ABC would coincided with V'
    ( After discussion, please tick "4 center" to show it.)