Polygons What is a Polygon

Welcome to Math with Mr. In this video, I'm going to go through what makes polygon polygon. So, basically, what is polygon? And it's plane, closed figure made of line segments. So, we're going to break that definition down and make it little easier and simpler. Now, when it comes to polygons, there's checklist, and polygon has to have check next to each of these three characteristics. So, we're going to go through what those three characteristics are. But before start that, when it comes to polygons, they have specific names. So, for example, three-sided polygon is triangle, four-sided polygon would be quadrilateral. I'm going to go through those specific names in another video. dropped that link down in the description. So, let's get back to what makes polygon polygon. So, the first characteristic or thing in our checklist, plane figure or plane shape. That just means the figure or shape has to be flat. So, if it's three-dimensional, like cube, pyramid, rectangular prism, those are not polygons. So, again, has to be flat. Next, closed. So, closed figure or shape. And that's exactly what it sounds like. It has to be closed. So, will give you counterexample that's not polygon. So, let's say we almost have rectangle here, but we have this opening. That would not be polygon because it's not closed. So, not polygon. And then lastly, made of line segments. So, I'll put line segments here. This means that there cannot be any rounded edges. So, for example, actually counterexample, circle is not polygon. Yes, it's flat. Yes, it's closed, but it's not made of line segments. polygon has to have check next to each of these three things. So, not polygon. Another counterexample would be figure like this. It's looking like it will be rectangle, but we have rounded top here. So, not polygon because it's not made of all line segments. So, let's take look at the right-hand side of your screen here. We're going to go through five different figures and determine if they are polygons. So, the first one here, this rectangle, it's flat, it's closed, and it's made of line segments. So, it is polygon. Let's go over to the cube here. It is not flat. It is closed, and it is made of line segments, but remember, we have to have check mark next to all three characteristics. So, cube is not polygon because it's three-dimensional. We'll move down to this shape here, and we have an opening. So, that figure is not closed, so it is not polygon. Over to the oval here, it's flat, it's closed, but it's not made of line segments. So, it is not polygon. And then lastly, the unique shape down there at the bottom, it's flat, it's closed, and it is made of line segments, so it is polygon. So, there you have it. There's what makes polygon polygon. Hopefully, that helped. Thanks so much for watching. Until next time, peace.