A regular tetrahedron lias six edges of length a.(a) Show that two opposite edges, such as...

A regular tetrahedron lias six edges of length a.(a) Show that two opposite edges, such as OA and BC, are perpendicular to each other. (b) Use this property and the result obtained in Prob. 3.59 to determine the perpendicular distance between edges OA and BC.

Fig. P3.60