Given: ABCD is a quadrilateral. P, Q, R and S are the mid-points of the sides DC, CB, BA and AD respectively.
To Prove: PR and QS bisect each other.
Construction: Join PQ, QR, RS, SP, AC and
BD.
Proof: In ∆ABC,
∵ R and Q are the mid-points of AB and BC respectively.
Similarly, we can show that
Thus a pair of opposite sides of a quadrilateral PQRS are parallel and equal.
PQRS is a parallelogram.
Since the diagonals of a parallelogram bisect each other.
∴ PR and QS bisect each other.
ABC is a triangle right angled at C. A line through the mid-point M of hypotenuse AB and parallel to BC intersects AC at D. Show that:
(i) D is the mid-point of AC (ii) MD ⊥ AC (iii)
D, E, F are respectively the midpoints of the sides BC, CA and AB of a triangle ABC. Show that:
(i) BDEF is a parallelogram
(ii) DFEC is a parallelogram.