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°).
the little squares in each corner mean "right angle"
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Each internal angle is 90° |
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Opposite sides are parallel and of equal length (so it is a Parallelogram). |
Play with a rectangle:
images/geom-quad.js?mode=rectangle
Area of a Rectangle
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Area = a × b |
Example: A rectangle is 6 m wide and 3 m high, what is its Area?
Area= 6 m × 3 m
= 18 m2
Perimeter of a Rectangle
The Perimeter is the distance around the edges.
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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
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A rectangle has two diagonals, they are equal in length and intersect in the middle. |
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A diagonal's length is the square root of (a squared + b squared): Diagonal "d" = √(a2 + b2) |
Example: A rectangle is 12 cm wide, and 5 cm tall, what is the length of a diagonal?
d= √(122 + 52)
= √(144 + 25)
= √169
= 13 cm
Golden Rectangle
There is also a special rectangle called the Golden Rectangle:
9091, 9092, 9093, 9094, 9095, 9096, 9097, 9098, 9099, 9100