- chris cambré
The undersurface of a cell is formed bij three congruent rhombusses. The area of the rhombus is defined by its diagonals d and D.
theorem of Pythagoras
The left graphical shows the prism in a frontally view of the blue side surface. You can rotate the 3D view to view the prism and the surfaces from different points of view. The diagonal D is the hypotenusa of a rectangular triangle with rectangle sides r en 2x.