# Rectangles: Definition, Properties & Construction

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• 0:06 Rectangles
• 0:48 Right Angles
• 1:10 Sides
• 2:17 Drawing a Rectangle
• 3:24 Lesson Summary

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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

Watch this video lesson to learn a bit about rectangles. Learn why rectangles are the building blocks of many homes. Also, learn about the properties that make a rectangle unique from other shapes. Finally, learn how you can draw one.

## Rectangles

The formal definition of a rectangle is a four-sided flat shape with four right angles measuring 90 degrees. Informally, you can call a rectangle a stretched-out square. If you were to use a square as a workout tool where you grab the ends and pull, then the shape that you get when you pull the ends is a rectangle.

Also, rectangles are the building blocks of many homes. Picture older homes where they used bricks. What shapes are the bricks? Why, they are rectangles. I remember when I was a kid, I used to play with building blocks that stacked and snapped together. Once I finished building something, I would look and see all kinds of rectangles making up the wall.

## Right Angles

Inherent in the definition of a rectangle is the property that a rectangle has four right angles. Yes, all of the angles of a rectangle measure 90 degrees. If you have a protractor on hand, you can measure each corner of a rectangle to check this.

No matter how long or short our rectangle is, it will always have four right angles.

## Sides

Because a rectangle has four right angles, it also has the property that the opposite sides are parallel and equal in length to each other. Look carefully at a rectangle, and you will see that one pair of opposite sides is usually longer than the other pair. If you think about a rectangle as a stretched-out square, you will see why. If you stretch out a square by pulling on its ends, you will see one pair of opposite sides get longer than the other. It is possible for a rectangle to have all its sides be the same length, in which case you would also call it a square.

Because of the rectangle's parallel sides, you are able to stack them without the top rectangles sliding off. Think about bricks and how you can keep building on top of them. Because bricks are rectangles, you trust that each brick you use will have a flat, level surface as long as the surface you are building on is also a flat, level surface. What if the sides of a brick weren't parallel? What would happen to the building? I picture the building slanting and then slowly crashing apart.

## Drawing a Rectangle

Let's talk about drawing a rectangle.

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