OP Malhotra Notes on Rectilinear Figures Class-9 S.Chand ICSE Maths 2026-27. We Provide Step by Step Answer on Rectilinear Figures, parallelogram and quadrilateral OP Malhotra Maths. Visit official Website CISCE  for detail information about ICSE Board Class-9.

OP Malhotra Notes on Rectilinear Figures Class-9 S.Chand ICSE Maths

Rectilinear figure :

Rectilinear means along a straight line or in a straight line or forming a straight line. Basically, it is a plane figure bounded by line segments.

Polygon :

Polygon is a closed rectilinear figure. The line segments by which it is bounded are called its sides, the points of intersection of consecutive sides are called its vertices, and the angle formed by the intersection of two consecutive sides is called an interior angle or simply an angle.

Regular and Irregular Polygons:

A regular polygon is equiangular and equilateral. The word equiangular means, the interior angles of the polygon are equal to one another. The word equilateral means, the lengths of the sides are equal to one another. The polygon with unequal sides and unequal angles is called an irregular polygon.

Practice Questions on Rectilinear Figure :- Exercise-11(a)

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Parallelogram

A parallelogram is defined as a simple quadrilateral in which both pairs of opposite sides are parallel.

Properties of a Parallelogram

Equal Opposite Sides : Both pairs of opposite sides are equal in length (AB = DC and AD = BC).
Equal Opposite Angles : Both pairs of opposite angles are equal (∠A = ∠C and ∠C = ∠D).
Supplementary Adjacent Angles : The sum of any two adjacent (consecutive) angles is exactly 180° (∠A+∠B = 180°, ∠B+∠C = 180°, etc.).
Bisecting Diagonals : The two diagonals intersect and bisect each other (cut each other into two equal parts).
Congruent Triangles : Either diagonal divides the parallelogram into two congruent triangles (ΔABD≅ΔCDB).

Practice Questions on Parallelogram :- Exercise-11(b)

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Quadrilaterals :

A quadrilateral can be defined as a closed, two-dimensional shape that has four straight sides.

Concave and Convex Polygons:
We know that each side of a polygon is connected by two consecutive vertices of the polygon. A diagonal is a line segment that connects the non-consecutive vertices of a polygon. If a diagonal lies outside a polygon, then the polygon is called a concave polygon. If all the diagonals lie inside the polygon, then the polygon is said to be a convex polygon.

Practice Questions on Quadrilateral :- Exercise-11(c)

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Construction on Quadrilateral

Constructing a quadrilateral requires a ruler, a compass, and a sharp pencil.

Step 1: Draw the base line segment of the given length.
Step 2: At the end points, use a protractor or a compass to construct the two given base angles.
Step 3: Mark the given lengths of the adjacent sides along the arms of the angles.
Step 4: Construct the third given angle at the new vertex and extend its line to intersect with the remaining side.

Rectilinear Figures :

• A plane figure bounded by line segments is called a rectilinear figure.
• A closed plane geometrical figure bounded by at least 3 line segments is called a polygon.
• The line segments forming a polygon intersect only at end-points and each end-point is shared by only two line segments.
• On the basis of sides, the polygons are classified as triangles, quadrilaterals, pentagons, hexagons, etc.
• A convex polygon is defined as a polygon with each of its interior angles less than 180°.
• A concave polygon is defined as a polygon with one or more interior angles greater than 180°.
• A polygon is said to be a regular polygon, if all its interior angles are equal, sides are equal and exterior angles are equal.
• The sum of all the interior angles of a convex polygon of n sides is (2n – 4) right angles.

Practice Questions on Construction on Quadrilateral :-  Exercise-11(d)

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In this chapter, we study all the topics on Rectilinear Figures and do some practice questions also. Here we solve extra practice questions on this chapter for better understanding.

Here is the link for extra practice questions on Rectilinear Figures :- Chapter Test

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— : End of Rectilinear Figures OP Malhotra S Chand Solutions :–

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