# Rectangle

## Definition

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

## Properties

1. Has four sides and four angles; in ▭ ABCD, AB, BC, CD, and DA are four sides and ∠ABC, ∠BCD, ∠CDA, ∠DAB are four angles
2. Opposite sides are equal; so AB = CD and BC= DA
3. Opposite sides are parallel; AB ∥ CD and BC ∥ DA
4. All the angles are 90°; in ▭ ABCD, ∠ABC = ∠BCD = ∠CDA =∠DAB =  90°
5. The diagonals are equal and bisect each other; so AC = BD
6. The sum of the interior angles is equal to 360 degrees; ∠ABC + ∠BCD + ∠CDA  + ∠DAB = 360°

## Formulas

### Diagonal

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

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.

As we know,
Diagonal (d ) = √(w 2 + l 2), where w = 12 cm and l = 5 cm
= √(122 + 52)
=√(144 + 25)
= √169
= 13 cm

### Area

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

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.

As we know,
Area (A) = w × l, where w = 10 cm and l = 6 cm
= 10 × 6 cm
= 60 cm2

### Perimeter

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