reserve SAS for Semi_Affine_Space;
reserve a,a9,a1,a2,a3,a4,b,b9,c,c9,d,d9,d1,d2,o,p,p1,p2,q,r,r1,r2,s,x, y,t,z
  for Element of SAS;

theorem Th99:
  trap a,p,b,q,o & trap a,p,c,r,o & not o,b,c are_collinear
  implies trap b,q,c,r,o
by Th98;
