NCERT Class 9 Solutions: Quadrilaterals (Chapter 8) Exercise 8.2 – Part 2 (For CBSE, ICSE, IAS, NET, NRA 2022)

Get unlimited access to the best preparation resource for IMO Class-9: fully solved questions with step-by-step explanation- practice your way to success.

  • Mid-point
The Triangle of ADE and EFC, in this Triangle the Mid Point …

In a triangle, the line segment that joins the midpoints of the two sides of a triangle is parallel to the third side and is half of it

Q-3 ABCD is a rectangle and P, Q, R and S are mid-points of the sides AB, BC, CD and DA respectively. Show that the quadrilateral PQRS is a rhombus.

Solution:

ABCD is a Rectangle Also PQRS is a Rhombus Quadrilateral
  • Give, ABCD is a ABCD is a rectangle and PQRS is a rhombus quadrilateral . P, Q, R
  • And S is mid-points of the sides AB, BC, CD and DA respectively.

In

  • P and Q are the mid-points of AB and BC respectively
  • Thus, and (Mid-point theorem) … equation (1)

In ,

  • S, R are the mid-points of AD and DC respectively
  • and (Mid-point theorem) … equation (2)

From equation (1) and (2)

  • So and

As in quadrilateral PQRS one pair of opposite sides is equal and parallel to each other, so, it is a parallelogram.

  • and (Opposite sides of parallelogram) … equation (3)

Now, In ,

  • Q and R are mid points of side BC and CD respectively.
  • Thus, and (Mid-point theorem) … equation (4)
  • (Diagonals of a rectangle are equal) … equation (5)

From equations (1) , (2) , (3) , (4) and (5) ,

  • So, PQRS is a rhombus.

Q-4 ABCD is a trapezium in which , BD is a diagonal and E is the mid-point of AD. A line is drawn through E parallel to AB intersecting BC at F (see Fig.) . Show that F is the mid-point of BC.

ABCD is a Trapezium

Solution:

  • Give, ABCD is a trapezium in which ,
  • BD is a diagonal and E is the mid-point of AD.
  • A line is drawn through E parallel to AB intersecting BC at F

Proof

  • F is the mid-point of BC.
  • BD intersected EF at G.
  • In ,
  • E is the mid-point of AD and also
  • Thus, G is the mid-point of BD (Converse of midpoint theorem)

Now, In ΔBDC,

  • G is the mid-point of BD and also GF || AB || DC.
  • Thus, F is the mid-point of BC (Converse of midpoint theorem)