# Rectangle

(Jump to Area of a Rectangle or Perimeter of a Rectangle)

A rectangle is a four-sided flat shape where every angle is a right angle (90°).

 means "right angle" are equal sides are equal sides
 Each internal angle is 90° Opposite sides are parallel and of equal length (so it is a Parallelogram).

Play with a rectangle:

## Area of a Rectangle

 Area = a × b

Area= 6 m × 3 m
= 18 m2

## Perimeter of a Rectangle

The Perimeter is the distance around the edges.

 The Perimeter is 2 times (a + b):Perimeter = 2(a+b)

### Example: A rectangle is 12 cm long and 5 cm tall, what is its Perimeter?

Perimeter = 2 × (12 cm + 5 cm)
= 2 × 17 cm
= 34 cm

## Diagonals of a Rectangle

 A rectangle has two diagonals, they are equal in length and intersect in the middle.
 A diagonal's length is the square root of (a squared + b squared):Diagonal "d" = √(a2 + b2)

d = √(122 + 52)
= √(144 + 25)
= √169
= 13 cm

## Golden Rectangle

There is also a special rectangle called the Golden Rectangle: