Q: 6 Show that the line segments joining the mid-points of the opposite sides of a quadrilateral bisect each other.
Given: ABCD is a quadrilateral in which P, Q, R and S are mid-points of the sides AB, BC, CD and DA. AC, BD are diagonals.
To prove: the line segments joining the mid-points of the opposite sides of a quadrilateral bisect each other.
Proof: In ACD,
S is the midpoint of DA. (Given)
R is midpoint of DC. (Given)
By midpoint theorem,
and ...................................1
In ABC,
P is the midpoint of AB. (Given)
Q is the midpoint of BC. (Given)
By midpoint theorem,
and .................................2
From 1 and 2, we get
and
Thus, and
So, the quadrilateral PQRS is a parallelogram and diagonals of a parallelogram bisect each other.
Thus, SQ and PR bisect each other.