RBSE Class 8 Maths Notes Chapter 3 Understanding Quadrilaterals

These comprehensive RBSE Class 8 Maths Notes Chapter 3 Understanding Quadrilaterals will give a brief overview of all the concepts.

RBSE Class 8 Maths Chapter 3 Notes Understanding Quadrilaterals

→ Any drawing (straight or non-straight) done without lifiting the pen may be called a curve.

→ A simple curve is one that does not cross itself.

→ A curve is said to be closed if its ends are joined; otherwise it is said to be open.

→ A simple closed curve made up of only line segments is called a polygon.

→ A diagonal is a line segment connecting two non-consecutive vertices of a polygon.

→ The sum of the measures of the external angles of any polygon is 360°.

→ If each angle of a polygon is less than 180°, it is called a convex polygon.

→ If at least one angle of a polygon is more than 180°, it is called a concave or re-extrant polygon.

→ A polygon is said to a regular polygon, if all its

• interior angles are equal;
• sides are equal;
• exterior angles are equal.

→ Number of diagonals in a polygon of n sides = [\(\frac{n(n-1)}{2}\) - n]

→ A polygon of n sides can be divided into (n - 2) triangles.

→ Each interior angle of a n-sided regular polygon = \(\left[\frac{(n-2) \times 180}{n}\right]^{\mathrm{c}}\)

→ Each exterior angle of a n-sided regular polygon = \(\frac{360^{\circ}}{n}\)

→ Number of sides in a regular polygon = \(\frac{360^{\circ}}{\text { Enterior angle }}\)

→ The sum of the angles of a quadrilateral is 360°.

→ If the sides of a polygon are produced in order, the sum of exterior angles so formed is always 360°.

→ Rectangle: A quadrilateral having its opposite sides equal and each angle measuring 90° is called a rectangle.

→ Square: A quadrilateral having all sides equal and each angle measuring 90° is called a square.

→ Parallelogram: A quadrilateral having its opposite sides parallel is called a parallelogram.

→ Rhombus: A parallelogram having all sides equal is called a Rhombus.

→ Trapezium: A quadrilateral in which a pair of opposite sides is parallel is called a trapezium

→ Kite: A quadrilateral having two pairs of equal adjacent sides, but unequal opposite sides, is called a kite.