What is a Rectangle? | Quadrilaterals | Math with Mr. J

[Music] Welcome to Math with Mr. J. In this video, I'm going to cover what a rectangle is. Now, simply put, a rectangle is a quadrilateral with four right angles. Let's take a look at some examples and dive in a little further. So, rectangles are quadrilaterals. They have four sides. Now, more specifically, rectangles are parallelograms. They have two pairs of parallel sides. Opposite sides are parallel and the same length. Opposite angles are the same measure as well. And then to take that a step further than just a parallelogram, rectangles have four right angles. So four 90° angles. So not only do rectangles have the features of quadrilaterals and parallelograms, all four angles are right angles. So looking at example A right here, we can see that we have a quadrilateral. This is also a parallelogram. Opposite sides are parallel and we can mark that using arrow symbols. So we'll use one arrow symbol on this side and one arrow symbol on this side to show that those sides are parallel. And then for the other pair of parallel sides, we will use two arrows to show that they are parallel. Opposite sides of a parallelogram and therefore rectangles are equal in length. So we can use tick marks to show that. So this side is the same length as this side. That one tick mark on each of those sides shows us that. And then we can use two tick marks on the other sides to show that they are equal in length. And then all four angles are 90°. And that's an example of a rectangle. Just remember rectangles are quadrilaterals with four right angles. And if we want to add to that, rectangles are parallelograms. They're just more specific or special parallelograms because all four angles need to be right angles. Let's move on to example B. Now here it looks like we have a square. So is this not a rectangle? Well, we have a quadrilateral and all four angles are right angles. So, let's mark that again. All four angles are right angles here. And then we know for a square, all of the sides are equal in length. So, we can use a tick mark on each side to show that they are all the same length. And this is a parallelogram as well. We have two pairs of parallel sides. We're not going to label those like we did for example A, though. So, is this a rectangle? Yes, this is actually technically a rectangle. When we hear rectangle, that tells us we have a quadrilateral with four right angles. And that's what we have here. So, yes, a square is a rectangle. A square is a quadrilateral with four right angles. Now, rectangle is not the best name here. It's not the most specific or fitting square is. We call this a square because that gives us more information about the shape. Not only do we have four right angles, but all of the sides are equal in length. Square tells us that we have all of the features of a rectangle, but all of the sides are equal in length as well. Basically, a square is a more specific or special rectangle. Let's move on to numbers 1 through 4 where we will determine if we have a rectangle or not. Green check mark means yes. Red X means no. Looking at number one, we have a quadrilateral with four right angles. So, yes, this is a rectangle. Now, all of the sides are the same length as well. So although this is a rectangle, the best and most specific name here is square. Moving on to number two, we have a quadrilateral and four right angles. So yes, this is a rectangle. Moving on to number three, we have a quadrilateral, but we don't have four right angles. So no, this is not a rectangle. And then lastly, number four, we have a quadrilateral with four right angles. So this is a rectangle. So there you have it. There's a basic overview of what a rectangle is. Just remember, a rectangle is a quadrilateral with four right angles. I hope that helped. Thanks so much for watching. Until next time, peace.