Mathematics and Origami
Once we know the co-ordinates of A, B, C, D, it is easy to obtain the length of BD and
AD:
BD= ()( )()xD−xB^2 + yD−yB^2 + zD−zB^2
AD= ()( )()xD−xA^2 + yD−yA^2 + zD−zA^2
Fig. 11 has the structure of a screw with four threads in it.
Interlude