## Definition

A plane figure with four straight sides making four right
internal angles.

## Properties

- Has four sides and four angles; in â– ABCD, AB, BC, CD, and DA are four sides and âˆ ABC, âˆ BCD, âˆ CDA, âˆ DAB are four angles
- Opposite sides are equal; so AB = CD and BC= DA
- Opposite sides are parallel; AB âˆ¥ CD and BC âˆ¥ DA
- All the angles are 90Â°; in â– ABCD, âˆ ABC = âˆ BCD = âˆ CDA =âˆ DAB = 90Â°
- The diagonals are equal and bisect each other; so AC = BD
- The sum of the interior angles is equal to 360 degrees; âˆ ABC + âˆ BCD + âˆ CDA + âˆ DAB = 360Â°

## Formulas

The line segments linking opposite vertices or corners of the rectangle. The formula is given below:

**Diagonal (***D*) = âˆš*w*^{2} + *l*^{2}, here w = width, l = length

**Problem**: Finding the diagonal of a rectangle when the **WIDTH **and** LENGTH** are known

**Find the diagonal of a rectangle whose width is 12 cm and length is 5 cm.**

Solution:

As we know,

**Diagonal (***d* ) = âˆš(*w*^{ 2} + *l*^{ 2}), where *w* = 12 cm and *l* = 5 cm

= âˆš(12^{2} + 5^{2})

=âˆš(144 + 25)

= âˆš169

= 13 cm

The total space enclosed by the rectangle. The formula is given below:

**Area (***A*) = *w *Ã— *l*, here w = width, l = length

**Problem**: Finding the area of a rectangle when the **WIDTH **and** LENGTH** are known

**Find the area of a rectangle whose width is 10 cm and length is 6 cm.**

Solution:

As we know,

**Area (***A*) = *w* Ã— *l*, where *w* = 10 cm and *l* = 6 cm

= 10 Ã— 6 cm

= 60 cm^{2}

The total distance covered around the edge of the rectangle. The formula is given below:

*Perimeter (P)* = *2(w + l)*, here w = width, l = length

**Problem**: Finding the perimeter of a rectangle when the **WIDTH **and** LENGTH** are known

**Find the perimeter of a rectangle whose width is 7 cm and length is 9 cm.**

Solution:

As we know,

**Perimeter (***P* ) = 2 (*w* + *l* ), where*w* = 7 cm and *l* = 9 cm

= 2(7 + 9) cm

Â = 2 Ã— 16 cm

= 32 cm