Pyramid Section (AR Modeling Challenge)
In this GeoGebra Augmented Reality Modeling challenge, the goal is to author 2 surface equations (with domain restrictions) to recreate what is seen in the screencast below.  
The blue surface consists of 4 congruent isosceles trapezoids. 
The pink surface is a square.  
Modeling Clues: 
1) If the non-parallel edges of  the 4 blue isosceles trapezoids were to extend upwards, they would all meet 
     at (0,0,5).  That is, these 4 isosceles trapezoids are part of a square pyramid whose apex lies at (0,0,5).
2) Suppose the height of this pyramid (described in (1)) = h.  Suppose the distance from the center of the 
     base of this pyramid to a vertex of this base = r.  Here, in this screencast, we have .  
3) The longer base of each isosceles trapezoid measures  units.