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Drawing perpendicular lines

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Subido el 22 de septiembre de 2013 por Samuel E.

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This video show the way of drawing perpendicular lines

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Hello, my name is Maria Miller from MathMyMoth.com. In this video we are going to study how to 00:00:00
draw a right angle and a rectangle. And this drawing a right angle is good for about third 00:00:05
grade math. Drawing a rectangle is both for third and fourth grade. And you need a tool 00:00:10
to do this and I am going to use a protractor first of all. Let's say here is your line 00:00:16
and you need to draw a right angle. It means you need to draw another line here that goes 00:00:23
at a right angle with your existing line. Okay? So you have to position your protractor 00:00:28
so that this is going to be where you're going to draw. You're going to draw along this line, 00:00:34
right? This side. And so just position your protractor so that your 90 degree mark here 00:00:38
lines up with your existing line and then the midpoint here, however it is marked, has 00:00:44
to line up with your line too. And then you just draw. So it's pretty simple. I'm going 00:00:49
to show you also how to do this same thing using a triangular ruler. This is a triangular 00:00:59
ruler and we can also use this to draw a right angle or actually to draw a line that goes 00:01:05
at the right angle called a perpendicular line. Again you need to use this side to actually 00:01:11
draw your line. So just position your ruler so that this corner here is exactly at your 00:01:18
existing line, and then you have to find your midpoint here, which in my ruler it is the 00:01:27
number 8 is marking the midpoint, so that has to line up too. Go exactly at the existing 00:01:31
line. There, and now I'm ready to draw the line. Okay, that makes a perpendicular line 00:01:38
and my right angle is of course here now. If need be, I could then erase this line or 00:01:45
whatever is needed to be erased. I'm going to change back to my protractor because that's 00:01:50
what I prefer. A common exercise that's given is to draw a perpendicular line or a right 00:01:55
angle so that it is at this given point, so that the line goes through this point. So 00:02:02
again, you're going to draw along this side. So just put this one here. Oh, I need to do 00:02:07
it this way this time and then line up the 90 degree mark over here with the 00:02:13
existing line there a little difficult okay like that here's my right angle oh 00:02:18
it could be that you have to draw your line so that it goes through a point 00:02:34
that is not on the existing line again you just have to line up you're gonna 00:02:38
draw over here and then you have to line up your 90 degree mark and the dot 00:02:43
and everything. It takes some practice to line up everything. Then you're ready to 00:02:51
draw. So here I could get my 90 degrees. Now you can also use this method to draw 00:02:57
a parallel line. Let's see how that goes about. I would first draw a line that is 00:03:04
perpendicular, a line that is at the right angle, then another line that is at 00:03:10
the right angle with my first line. Okay, first I will draw just any line that is 00:03:14
at the right angle, using the same method here. Now I will draw a line that is at the 00:03:20
right angle with this red line. Okay, I can't see my 90 degree mark, I better continue this 00:03:27
line some more here. Now I can line up my 90 degree mark here and then just draw a line 00:03:37
here. So I got the line that is parallel to the existing line. Of course there are other 00:03:47
methods for doing this too. But this is if you are allowed to use a protractor or a triangular 00:03:54
ruler. Lastly, we're going to draw a rectangle. And I wrote here 50 centimetres and 20 centimetres 00:03:58
because that's how big I have to draw it so that it won't be just a teeny one here on 00:04:06
the board. But for students who are drawing it on the paper, they need to use smaller 00:04:10
numbers because 50 centimetres would exceed paper size, so maybe 10 and 4 centimetres 00:04:14
or something like that. Now we will start out by drawing first the one side of the 00:04:19
rectangle and I need this for drawing the right angles and then a normal ruler 00:04:25
for drawing longer lines. So let's draw first a line then I need to measure on 00:04:31
it the 50 centimeters here and here and now let's draw a line that goes at the 00:04:44
right angle. The best we can, as accurately as we can. There. And on this side, there's 00:05:00
a lot of lining up to do and it is hard to be 100% accurate. So, don't be surprised if 00:05:18
these don't exactly match with, don't look like rectangles. Okay, I need my centimeters 00:05:30
here to measure 20. There, now I have marked the 20 cm and 20 cm. So, now I should be able 00:05:37
to just draw a line from here to here. And here's my rectangle. 00:05:57
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Idioma/s:
en
Etiquetas:
EducaMadrid
Autor/es:
MathMammoth
Subido por:
Samuel E.
Licencia:
Reconocimiento - No comercial - Compartir igual
Visualizaciones:
83
Fecha:
22 de septiembre de 2013 - 18:56
Visibilidad:
Público
Centro:
IES JOAQUIN ARAUJO
Duración:
06′ 21″
Relación de aspecto:
1.78:1
Resolución:
640x360 píxeles
Tamaño:
22.61 MBytes

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