ABCD is a rhombus and P, Q, R and S are the mid-points of the sides AB

Updated on November 25, 2023
by Tiwari Academy

In rhombus ABCD, with P, Q, R, and S as mid-points of sides AB, BC, CD, and DA respectively:
PQRS is a Parallelogram: By the Midpoint Theorem, PQ and SR are parallel and equal as they join midpoints of consecutive sides of the rhombus. Similarly, PS and QR are parallel and equal. Thus, PQRS is a parallelogram.
Angles in PQRS are Right Angles: In a rhombus, diagonals bisect each other at right angles. Since P, Q, R, and S are midpoints, they form right angles at the intersection of the diagonals.
Therefore, PQRS is a parallelogram with right angles, making it a rectangle.

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

Let’s discuss in detail

Rhombus ABCD and Midpoints

In the rhombus ABCD, points P, Q, R, and S are the midpoints of the sides AB, BC, CD, and DA, respectively. A rhombus is a special type of parallelogram where all sides are equal, and its diagonals bisect each other at right angles. The positioning of midpoints on the sides of a rhombus creates a unique geometric configuration. This setup allows for the exploration of the properties of the quadrilateral formed by connecting these midpoints, leading to insights into the nature of this quadrilateral, PQRS, within the context of the properties of a rhombus.

PQRS as a Parallelogram

Firstly, it’s important to establish that PQRS is a parallelogram. According to the Midpoint Theorem, a line segment joining the midpoints of two sides of a triangle is parallel to the third side and half its length. Applying this theorem to the triangles formed by the diagonals of the rhombus, it can be deduced that PQ is parallel to SR and PS is parallel to QR. Since opposite sides are parallel, PQRS satisfies one of the key criteria for being a parallelogram.

Equal Lengths of Opposite Sides in PQRS

In addition to being parallel, the opposite sides of PQRS are also equal in length. This is again a result of the Midpoint Theorem. In a rhombus, all sides are equal, so when midpoints are connected, the lengths of PQ and SR, and PS and QR, are equal because they each span half the length of the sides of the rhombus. This equality of opposite sides further confirms that PQRS is a parallelogram.

Right Angles in PQRS
A defining feature of a rectangle is the presence of right angles. In a rhombus, the diagonals bisect each other at right angles. Since P, Q, R, and S are midpoints of the sides of the rhombus, they lie on the diagonals. Therefore, at the point where the diagonals intersect, which is inside PQRS, right angles are formed. This means that each angle in PQRS is a right angle.

PQRS as a Rectangle

Given that PQRS is a parallelogram with right angles, it meets the definition of a rectangle. A rectangle is a parallelogram with right angles, and since PQRS has been shown to have both these properties, it can be conclusively stated that PQRS is a rectangle. This conclusion is a direct result of the properties of the rhombus ABCD and the specific positioning of the midpoints on its sides.

Geometric Nature of PQRS

In conclusion, the quadrilateral PQRS, formed by connecting the midpoints of the sides of rhombus ABCD, is a rectangle. This is established through the application of the Midpoint Theorem and the properties of a rhombus, specifically the behavior of its diagonals. The exercise demonstrates how specific configurations within a geometric figure can lead to the formation of another figure with its own distinct properties, showcasing the interconnectedness and elegance of geometric principles.

Discuss this question in detail or visit to Class 9 Maths Chapter 8 for all questions.
Questions of 9th Maths Exercise 8.2 in Detail

ABCD is a quadrilateral in which P, Q, R and S are mid-points of the sides AB, BC, CD and DA. AC is a diagonal. Show that: (i) SR || AC and SR = 1/2AC (ii) PQ = SR (iii) PQRS is a parallelogram.

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

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.

ABCD is a trapezium in which AB || DC, 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. Show that F is the mid-point of BC.

In a parallelogram ABCD, E and F are the mid-points of sides AB and CD respectively. Show that the line segments AF and EC trisect the diagonal BD.

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) CM = MA = 1/2AB.