**Area:-** The area of a plane figure is the total space enclosed by its boundary. It is always expressed in square units.

**Perimeter:- **Sum of the length of the border around a plane figure is known as the perimeter of that plane figure.

**Rectangle:- ** It is a four-sided closed figure with equal opposite sides. Each angle of it is \(90^\circ.\)

**Area of a Rectangle:- **

**Area of a rectangle** = **Length x Breadth** = **ab**

**Length** = \(\frac{\textbf { Area }}{\textbf { Breadth }}\) and

**Breadth = \(\frac{\textbf { Area }}{\textbf { Length }}\)**

**Perimeter**** of the rectangle:- **

** Perimeter of the rectangle = 2(Length + Breadth)**

**Diagonal of a Rectangle:- **Line segment joining the contrasting corner of the rectangle is known as diagonal of the rectangle. In the adjacent figure, AC is the diagonal of the rectangle.

i.e. **Diagonal of a rectangle = \(\sqrt{(\textbf { Length })^{2}+(\textbf { Breadth })^{2}}\) = \(\sqrt{a^{2}+b^{2}}\)**

**Square:- ** It is a four-sided closed figure with all sides equal.

**Area of a Square:- **

** Area of a square = \((\textbf { Side } )^{2}\) = \((a)^2\)**

** the side of a square = \(\sqrt{\textbf { Area }}\)**

**Perimeter of a Square:- Perimeter of a square = 4 x side = 4a**

**Diagonal of a Square:- **Line segment joining the contrasting corner of the square is known as diagonal of the square. In the above figure, AC and BD are the diagonal of square ABCD.

** Diagonal of a Square = \(\sqrt{2}\) x side = \(\sqrt{2}\)a**