The graph of f confirms the calculated extremum and shows that it's a minimum.[br][list][*]Change the value of h and see if it influences the extremum.[br][/*][*]Change the value of r and see of the calculated value still matches the graph.[/*][/list]

The area of the cell gets minimal if x = [math]\frac{\sqrt{2}}{4}[/math] . r.[br]With this value we can calculate [br][list][*]the diagonals d and D[/*][*]the angles of the rhombusses [br][/*][*]the angles between the rhombusses and the horizontal plane[/*][/list]