some theorems on strict betweenness relations
Let be a strict betweenness relation. In the following the sets are defined in the entry about some theorems on the axioms of order.
Theorem 1.
Three elements arein a strict betweenness relation only if they are pairwise distinct.
Theorem 2.
If is strict, then , and are pairwise disjoint.Furthermore, if then all three sets are empty.
Theorem 3.
If is strict, then and .
Theorem 4.
If is strict, then for any , , , and are infinite.