Angles Basics - Free Educational videos for Students in K-12

Angles Basics - By tecmath

Transcript


00:0-1	Good day . Welcome to Tech Math Channel . What
00:02	we're going to be having a look at in this
00:03	video is we're going to have a look at angles
00:05	. Okay . That is , we don't like the
00:07	basics of them , what they are types of angles
00:11	as well as terminology that we use when we talk
00:13	about angles as well as the properties of different angles
00:16	. Okay , so let's launch into this first off
00:20	, let's consider two lines here . So I'm gonna
00:22	put two lines up and my two lines are here
00:26	. You see two lines , I'm gonna right these
00:29	lines as that . We name them . Okay .
00:31	We would call these lines A . B and we
00:34	would write it like this and we would call this
00:36	second line C . D . Okay . And we
00:39	write them by writing the points of the lines A
00:42	and B . And we put the line over the
00:43	top to show that we're talking about a line .
00:45	So you've got these two lines , A , B
00:47	and C . D . Now , if you were
00:49	to look at these lines , you might look at
00:50	them and realize they're running in the same direction .
00:53	These guys could go on forever and ever and ever
00:55	and they would never cross . Okay , so lines
00:58	like this are said to be parallel , I'll write
01:02	it down . These are parallel . Lawrence . Yes
01:07	. The thing about parallel lines they denoted . First
01:09	off , we put little arrows like this to denote
01:12	that we're actually talking about parallel lines , but these
01:15	guys will never cross that will never form angles with
01:19	each other . Okay , so we write that these
01:21	guys are paralleled by putting this particular symbol between them
01:25	. So these guys you go , wait a second
01:27	. Why don't you to introduce us into angles by
01:30	showing us something which doesn't form angles ? Well ,
01:33	I'll tell you why , because I'm going to show
01:34	you now what happens if we move these lines a
01:36	little bit and we let them cross . So what
01:38	we do is we end up with a situation like
01:41	this . We have our lines uh abe and we
01:46	have our second line which is Cd . But now
01:50	these guys a moves , they do cross . And
01:52	you're going to notice that where they cross . They
01:54	have this particular point here . This particular point is
01:57	called an intersection . Ah You might be thinking ,
02:00	okay , I've heard that word before . An intersection
02:02	like where two roads cross one another is called an
02:05	intersection . And it's a similar sort of word .
02:08	I'm going to label this particular point where they cross
02:12	zero . So what you might notice when we have
02:15	a look at this is that now that our lines
02:18	are crossing , we have these points in between our
02:21	lines . Okay , I'll show you we have this
02:23	part here . This little gap in between the intersection
02:26	line . We have a little gap in between the
02:27	intersecting lines . This one and this one we have
02:30	a gap between these two intersecting lines . And we
02:32	have a gap between these two intersecting lines . And
02:35	these gaps we call angles . Okay so first off
02:42	, how do we go about describing these angles ?
02:45	Now describing angles is really , really simple . There's
02:47	a couple of ways we can do it . First
02:49	off , we can describe angles based upon the or
02:53	name angles based upon the points that we're talking about
02:56	to say I was talking about this angle here .
02:57	So I've got a line going here . We've got
03:00	the intersection and I got on the line . Go
03:02	up here . We would call this angle with do
03:05	this little symbol of the night . We're talking about
03:07	an angle we would call it . We're starting at
03:09	the we're going through the intersection . Oh and then
03:12	going to the D . So we actually call this
03:14	A . And just to show that that's where the
03:19	I was from . I will change a different color
03:20	there . Indeed . This is angle A . O
03:24	. D . You don't have to put those in
03:25	different colours . I'm just doing that to give you
03:27	a bit of a hand when you do these .
03:28	Okay , so that's how we name these angles .
03:31	I'll give you another example of it . Say I
03:33	want to name this particular angle here . I'm starting
03:36	with A . D . I'm going through the oh
03:39	and I go to the beast . I'm talking about
03:40	this angle here . D . O . B .
03:44	Oh right . This is angle T . I would
03:47	put the O . Down . Okay , the intersection
03:50	part and I will put the baby down again .
03:53	You don't have to go different colors . But we've
03:55	got the angle D . O . B . That's
03:58	the way that we can name angles you'd see here
04:00	that we actually have four different angles that we can
04:02	name . Okay when I was going to do to
04:04	, that's one of the ways that we can name
04:06	angles . There's another way of identifying angles in a
04:09	diagram . And this is this way occasionally what you
04:13	might do this these angles is you might just put
04:16	them down as a letter . Okay . So for
04:20	instance I will get rid of all our letters there
04:24	. So we don't foresee any confusion and imagine I'm
04:28	just going to mark on this is the way we
04:29	market . We do this little circular part called an
04:32	arc . Okay . And I can actually just put
04:35	a letter in there instead . So say and I
04:38	could call this angle I . Or another one I
04:43	could do is I could be talking about this angle
04:47	and I could call this one B . And I
04:49	would write this down as angle B and so on
04:51	and so forth . So that's the way that we
04:54	go about naming angles . So that's that part done
04:59	. Now . I'm just going to get onto some
05:01	different types of angles that we get when we actually
05:04	make angles . So let's get rid of all of
05:07	this . In fact I might just leave that center
05:11	line there . Okay , so get rid of that
05:15	little part there . And now I'm going to just
05:17	put on one more particular line . One little line
05:21	here say my line comes down and it comes down
05:25	so the lines meet like this . So the angles
05:28	here that we have are exactly the same size .
05:31	This is cutting straight through . Okay , this angle
05:35	is the same as this angle and this angle is
05:38	the same as this angle . In fact , all
05:39	the angles are of the same size . Okay ,
05:42	so I could even go and call this one .
05:45	Yeah , I the see D and I can say
05:52	here that angle and I'll put this , oh here
05:55	again . I could say the angle A O C
05:58	. Is the same as angle A O . D
06:01	. Or I could say angle D . O B
06:03	is the same as angle A . O . D
06:04	. They're all the same . Okay . Lines that
06:07	meet like this first off have a special name .
06:10	These lines are said to be perpendicular . Okay ,
06:14	I'll write that one down , pen particular . Okay
06:21	. And where these guys actually meet , you'll see
06:26	that they form these square looking angles . Okay ,
06:28	so we call these particular square angles . These are
06:31	a really special type of angle that we call .
06:34	Right angles . Okay . Right angles . All right
06:40	. And quite often we show these right angles by
06:43	putting this little square shape down here . Okay ,
06:46	This square symbol we put rather than this are So
06:48	have you ever seen this little square symbol here ?
06:50	It means that you're talking about a right angle .
06:52	Okay . And it's one of these angles that occurs
06:56	exactly like the edge of a square , on the
06:58	edge of a rectangle . Okay , so I'm just
07:02	gonna get rid of this , and I'm gonna just
07:03	draw this particular right angle , just so we can
07:08	use it to describe some other types of angles .
07:11	So , first off , I'll draw the up and
07:16	down line the vertical line , and I'll draw this
07:20	horizontal line here . And I don't draw this particular
07:24	shape here to show that it is a right angle
07:27	. Okay , so straight away , if you see
07:29	this , you know it's a right angle . But
07:31	say I was to change my right angle a little
07:34	bit and I was to actually now decrease the arm
07:37	of this right angle in a little bit . Okay
07:40	? And I was decrease it . So instead of
07:42	what we were instead of having this particular line here
07:45	, it was now coming in less than that right
07:49	angle , it was coming in at this angle .
07:52	Instead a car go back to using this rounded shape
07:56	to denote the angle . And what we do is
08:00	we basically angles like this , which are less than
08:02	right angles , angles which are under the right angles
08:06	between zero and the right angle shape are said to
08:09	be acute angles . Okay , acute angles . So
08:15	any angle uh this sort of shape is said to
08:19	be an acute angle . This is our second type
08:21	of angle . So we first off our right angle
08:23	and they've got the angles that a lesson right angles
08:26	that are smaller than right angles . An appointee of
08:27	the right angles , I guess you can think about
08:29	them as being acute angles . Okay , so a
08:33	third type of angle we're gonna have a look at
08:35	now is an angle where we increase the size of
08:41	our arms . Okay ? Our arms get further and
08:43	further apart . Okay . And the angle gets bigger
08:46	than a right angle . In fact , our angle
08:48	gets like this okay , it opens up , it's
08:53	bigger than a right angle angles like this . Okay
08:56	, I'll mark on our angle here an angle like
08:59	this is said to be abuse . This is an
09:03	obtuse angle . Okay , so we have three types
09:09	of angles so far . Okay , and I'll draw
09:11	these freehand just so you can remember them okay .
09:14	They won't be the not necessarily the nastiest , the
09:16	nicest drawings , but we'll see . We have the
09:18	first one Which is like this , these ones under
09:22	90°. . These are said to be acute and the
09:25	way that you can read these is they're they're small
09:27	, they're cute . Yeah , we have the right
09:29	angle . Okay , again , this should be nice
09:33	and square . Like the edge of the square .
09:35	This is said to be right and we have this
09:39	choose angle . Okay , abuse . And of course
09:44	when you were doing these you would never draw anything
09:46	so messy as me . But I'm trying to be
09:48	a little bit quick when I draw them as well
09:50	. Uh not that that's any sort of excuse whatsoever
09:53	. Okay , so the arm is going to go
09:56	into a couple of final type of angles and these
09:59	are those Okay , so we can extend the arms
10:02	of an angle right out to say I have my
10:07	point there which the angles are coming from the point
10:09	by the way , if I'm just drawing the angle
10:12	by itself and I say I have an angle like
10:14	this and I'm just drawing the point by itself .
10:16	This point here is no longer said to be an
10:18	intersection intersections are where the lines cross . But now
10:22	we're just talking about the point . These are said
10:24	to be a vertex . All right , that in
10:26	this is a vertex . Okay , this particular point
10:30	there . Okay , let's say I was to from
10:33	my vertex there . I was to increase the arm
10:36	so it opened right out . In fact , it's
10:38	going to rope and right out to the point where
10:40	I have a straight line and this is my angle
10:44	here . Now this particular angle , you might be
10:50	really , really unsurprised to hear . It's formed a
10:52	straight line and it's called a straight angle . A
10:57	straight angle . Okay , So now we've got 1/4
11:01	type of angle . The last type of angle which
11:04	I'm going to talk about is where we go beyond
11:07	that straight line . Okay . And what we do
11:11	is how to slow this down a little bit .
11:15	We'll move that up a bit and we have this
11:18	particular circumstance where we go right around . Okay .
11:22	We've gone beyond the size of the straight angle and
11:25	we're now we're in the realm of going all the
11:27	way possibly back to the original part here . This
11:32	is called a reflex angle . A reflex angle .
11:35	Okay , A reflex . So that's it . For
11:41	now we have five different types of angles . Hopefully
11:45	this has been a really good little staff for when
11:47	we talk about angles . Okay . A couple of
11:49	key terms to remember is that you have these arms
11:53	here . You have if the line's intersection , you
11:55	have an intersection , you have those idea of parallel
11:58	and perpendicular lines , you have the different types of
12:00	angles and also this idea of a vertex here in
12:04	the next video , I'm gonna be making , we're
12:06	going to have a look at how to measure these
12:08	angles and how to get them . You know how
12:10	we know exactly how big they are and we're gonna
12:13	be talking about these and going over these and choose
12:15	an acute angles again and how many , how big
12:18	each one of these are . So anyway , I
12:20	hope you watch that video that's coming up there .
12:24	And I thank you for watching this video . We'll
12:26	see you later . Bye .

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Angles Basics is a free educational video by tecmath.

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