Common perpendiculars to lines in space: common

The common_perpendicular command finds the common perpendicular to two lines.

common_perpendicular takes two arguments:
L,M, two lines.
common_perpendicular(L,M) returns and draws the common perpendicular to L and M.

Example.
Input:

L1:= line(point(1,1,0),point(0,1,1)):;

L2:= line(point(0,-1,0),point(1,-1,1)):;

common_perpendicular(L1,L2)

Output: