(i)Prove that every line segment has one & only one midpoint.

 

 

(ii)In the given figure are exterior angles of quadrilateral ABCD at point B & D &

Show that a line segment has one and only one mid-point.

Proof: Let point R be teh mid point of line segment PQ.

Let if posssible, O be another mid-point of PQ.

PO = OQ       ....(1)

But, it is given that R is the mid point of PQ.

PR = RQ       ....(2)

Subtracting (1) from (2), We get 

Therefore, O and R must coincide.

Thus, every line segment has only one mid-point.