Math Antics - Polygons - Free Educational videos for Students in K-12

Math Antics - Polygons - By

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00:03	Uh huh . Hi there . Welcome to Math Antics
00:08	so far in our series in geometry , we've learned
00:10	about points , lines , planes and angles . In
00:14	this lesson , we're going to learn about another important
00:16	element of geometry . We're going to learn about polygons
00:19	. You probably already know a lot about polygons because
00:23	you see them all the time . Here are some
00:25	common examples that you might recognize . These shapes are
00:29	all polygons . That's because of polygon just means a
00:32	multi sided shape and these shapes all have multiple sides
00:37	. Okay , so that's a basic definition of a
00:39	polygon . But to really understand what is a polygon
00:43	and what is not a polygon . We need to
00:45	learn about the specific properties that all polygons have in
00:49	common . First , we need to know the three
00:51	parts that make up all polygons . And these parts
00:54	are sides vortices and angles . The sides are just
01:00	the straight line segments that make up a polygon and
01:03	the vertex is are the points where the sides intersect
01:07	and the angles are formed by the intersecting lines .
01:10	In fact in greek , the word polygon literally means
01:14	many angles . So all polygons have sides advertises and
01:19	angles . This polygon here has five sides , five
01:22	verses and it forms five angles . The next thing
01:26	we need to know about polygons is that they're closed
01:28	shapes . Now , what does it mean for a
01:30	shape to be closed ? You ask . Well it
01:33	means that the sides are connected so that there are
01:35	no gaps . The area inside , the shape is
01:38	separated from the area outside the shape and there's no
01:42	way to get from the inside to the outside without
01:44	crossing the line . It might help to think of
01:47	a close shape like a cage . If you put
01:50	an ant inside the cage then there's no way for
01:53	it to get out without crossing the line . But
01:56	if the shape is open then there is a way
01:58	out . So these are all examples of closed shapes
02:02	. And these are all examples of open shapes .
02:04	And the important thing to remember is that a polygon
02:07	must be closed . And the last thing we need
02:10	to know about polygons is that they're two dimensional or
02:13	flat shapes . And that means that all the vertex
02:16	is must lie on the same plane . If any
02:19	one of the vertex is were to move forwards or
02:22	backwards so that it wasn't on the same plane as
02:24	all the other vertex is . Then it wouldn't be
02:26	a flat shape anymore . Flat shapes are also called
02:29	cleaner shapes because all of their points are on the
02:33	same plane . And even though polygons themselves can't be
02:36	three D shapes , you can use polygons to make
02:39	three D shapes like a box . For example ,
02:42	the box is not a polygon , but each of
02:45	its flat sides is a polygon . All right then
02:50	we now have a specific definition of a polygon .
02:53	The polygon is a multi sided shape that has sides
02:56	, verte sizes and angles . A polygon is a
02:59	closed shape and a polygon is a two dimensional or
03:03	a flat shape . And now that you know that
03:06	it's time to play polygon or not a polygon .
03:10	Now here's your host , me . Thank you .
03:14	Thank you . All right now the rules of the
03:17	game are simple . I'm gonna show you a shape
03:19	and you tell me if it's a polygon or not
03:22	a polygon , are you ready to play ? Our
03:26	first shape is a square , is a square polygon
03:31	. Yes square has four sides and four advertises .
03:35	And it's a closed two D . Shape . So
03:37	it is a polygon . And next we have but
03:43	not exactly sure what to call this . But is
03:46	it a polygon , nope , it's close but because
03:49	it's an open shape , it can't be a polygon
03:53	. All right . What about this one , polygon
03:56	or not polygon , yep . It is a polygon
04:01	even though the sides aren't all the same length .
04:03	It is a closed two D . Multi sided shape
04:06	. In fact if you count you'll see that .
04:08	It has seven sides . What about this one ?
04:14	Is a circle of polygon ? Well it is a
04:17	closed two D . Shape but how many sides does
04:21	it have ? Now ? That's the problem . A
04:24	circle doesn't have any straight sides advertises or angles .
04:28	It's a curved shape . So it's not a polygon
04:31	. Next we have a star shape just like me
04:35	. Is it a polygon , yep , it has
04:39	straight sides advertises and it's a closed two D .
04:43	Shape . That means it's a polygon . And what
04:47	about this one ? Right , you are . This
04:50	is not a polygon , It's a dog . Uh
04:55	Here's an interesting one . It's a closed two D
04:58	. Shape that does have straight sides and vortices .
05:01	But it also has this curved part here . Can
05:05	it still be a polygon with that curve there ?
05:07	No the curved part disqualifies it as a polygon polygon
05:13	has to have only straight sides . So this is
05:18	not a polygon . And what about this guy here
05:21	? Is this a polygon ? Well it is just
05:23	straight lines but two of those lines cross and if
05:27	any lines cross it can't be a polygon . Plus
05:30	he has this big open in here . So this
05:32	guy is definitely not a polygon . And last of
05:36	all , what about this one ? Right . You
05:38	are this is not a polygon because it's a three
05:41	D . Shape . It's made from polygons . But
05:44	the whole shape is not a polygon itself . Well
05:48	that's all the time we have for this week ,
05:50	join us next week as we decide is it bigger
05:53	than one ? Okay so after playing that game you
05:58	should have a really good idea of what a polygon
06:00	is and what it is . Not . The last
06:02	thing I want to mention is that some polygons have
06:05	special names depending on how many sides they have .
06:08	Here is a list of the most important ones to
06:11	know . three sided polygons are called Triangles . Triangles
06:15	are so important in geometry that they'll get a whole
06:18	video of their own foresighted polygons are called quadrille laterals
06:24	, wow . Now that's a fancy math word But
06:27	it helps if you just remember that the first part
06:29	quad means four quadra laterals are shapes like squares ,
06:34	rectangles and parallelogram . They'll also get a video of
06:38	their own five sided polygon are called Pentagon's six sided
06:43	polygons are called Hexagons . An eight sided polygons are
06:47	called Octagon , by the way , polygons that have
06:51	568 or however many sides like this are called regular
06:55	polygons . If all of their angles are equal and
06:58	irregular polygons , if their angles are not equal ,
07:02	of course there are a lot more polygons than that
07:05	, but you probably won't need to know their names
07:08	as long as you know what polygons are and how
07:11	to identify them , then you're ready to move on
07:14	. The exercises for this section are pretty easy .
07:17	So no excuses . Good luck . Thanks for watching
07:20	Math Antics and I'll see you next time learn more
07:24	at Math Antics dot com .

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