theorem
  not o1 on O1 & not o1 on O2 & not o2 on O2 & not o2 on O3 & O1,O2,O3
are_concurrent & O1<>O3 implies ex o st not o on O1 & not o on O3 & IncProj(O2,
  o2,O3)*IncProj(O1,o1,O2) = IncProj(O1,o,O3)
by PROJRED1:25;
