To identify angles inside 2D shapes

Key Stage 2

Maths

Angles and shape

An angle is created when a pair of lines run next to each other but never touch.

An angle is the space created between a pair of intersecting lines.

Which images show an angle being formed? (3 answers)

Which symbol compares the angle sizes correctly?

﻿Hi year three, it's Mr. Etherton here. And welcome back to another day of our exciting maths learning. Today is lesson two of week four, and is our second lesson on our new unit on angles and shape. Today, our learning outcome is to be able to identify angles inside 2-D shapes. So we're going to be building on yesterday's learning and exploring a little bit further. So as always, let's be prepared for our learning. So in this lesson, we'll review what an angle is. We will begin to explore the various angles that are found inside 2-D shapes before noticing patterns between the number of sides and the number of angles. In order to complete today's learning, the equipment you need is a pencil. You need a piece of paper or an exercise book to do some working out. You might want a ruler as well, if you want to draw any of the shapes, that's absolutely fine. And again, today we will need an angle detector, if you still got it. If you haven't got an angle detector or didn't join in with yesterday's learning, I will show you what you need. To make your own angle detector, you need two strips of card like this, and you need a split pin, which looks like this. And then you need to put your two pieces of card together on top of each other. And then at one end, you need to push through your split pin and it will help to make your angle detector. And we will use this to help us explore the different angles that we see today. So it should look like this once it's complete, and we can move it around to the size of the different angles. So, let's start with today's learning. Today the first thing I would like you to do is to complete your introductory knowledge quiz. If you haven't completed this, can you pause the video now. If you have completed, continue watching. Brilliant year three. Let's have a look at our warm up activity. So, on the screen you can see that there are lots of different 2-D and 3-D shapes. These are represented as A, B, C, D, E, and F. On your piece of paper, can you draw a little table and split it into two columns, 2-D and 3-D shapes as your headings. Then I just want you to write the letters of the shapes and put them in the correct column, depending on whether they are 2-D or 3-D. I think you should have one minute to complete this activity, so pause the video now, off we go. Fantastic year three, welcome back. Let's have a look through our answers and we'll have a think, what are 2-D shapes and what are 3-D shapes? So, if we look at A, we can see, oh, what shape is it? Can you shout out, shape eight is a... Well done, it is a triangle. So you should have put A for triangle in 2-D shapes. We'll explain what the difference between the two are at the end. B, 2-D or 3-D? Shout out. Well done, it is a triangular prism, so it is a 3-D shape, well done. C, shout it out. Brilliant if you said it is 3-D. Well done, that's a tetrahedron, or you might know it is a triangular-based pyramid. It's a 3-D shape. D, well done if you said that it is a 2-D shape. E, fantastic, it is 3-D, a cube. And finally F, well done if you said that our pentagon was a 2-D shape. Can you look at my completed table now? What are the differences between 2-D and 3-D shapes? I can see a lot of you are thinking, our 2-D shapes have or got colours, our 3-D shapes do not. That is the example here, but actually 2-D shapes only have two dimensions. That means they have a height and a width. Whereas our 3-D shapes have three different dimensions. They also have a height, they also have a width, but they also have a depth. So there are different meanings for different types of shapes. So well done if you've remembered that learning. But let's explore more about our learning today. So my turn, your turn, repeats after me our star words please. Angle, property, turn, edge, vertices, and vertex. Thank you for joining in year three, let's have a quick look at what some of these words mean. So remember yesterday we were looking at different properties of shapes. So a property is a way that we can describe a shape. So we might be able to describe a shape by the number of sides it has, or the number of faces it has. But the property we're looking at our angles. An angle is a measure of turn. As well, we're going to be building a bit more on this and looking at how angles represent turns. And three words that are going to be very important today are going to be edge. So an edge are the sides of the shape. So, we were looking at angles and the two lines that would be an edge. And vertices, that means corners or points. And Vertex just means one corner or one point of a shape. And we use the corners and the edges to help us find our angle. So, what can you remember from yesterday's learning? On the board, I have three different definitions of what an angle is. I would like you to pause the video, read through them and decide whether you think definition A, B or C describes what an angle is. So pause the video now. Fantastic, welcome back year three. So I'm going to count down from three to zero and on zero can you shout the letter of the definition that describes an angle. Are we ready? Three, two, one, zero. Fantastic, I heard so many of you shouting out the letter A. Let's have a quick look and see if you were correct. Let's check. So it says A. An angle is the space created between two intersecting lines. So if we look at my picture, I have my two lines here. Intersecting means that they meet and yes they do. And we can represent the angle by the space between, well done. These two lines do create an angle. Are we sure it wasn't B though? Let's have a check. So B, an angle is when two lines run alongside each other. Well done, if you didn't say you B, because we can see here that our lines were next to each other, but to create an angle, they must meet to make a vertex or make multiple vertices. So it wasn't B. And C, it says an angle is when two lines pass through each other. This was a tricky one. You might have said C because I think some of you would have been able to see angles within these lines. But actually the definition, just when two lines pass through each other, that doesn't mean it's an angle. We could say that that is a definition for the word intersecting. When two lines meet or pass through each other, but that's not actually what an angle is. So well done. An angle is the space created between two intersecting lines. So, let's have a look at the shape on the board. And we're going to use an angle detector to help us work out where the different angles in this shape is. So on the screen, you can see a white rectangle, or we might have this represented as a piece of white paper. To be able to find an angle in a shape. We are going to use our angle detector. And remember an angle is a measure of turn. So, to be able to see the turn or the angles that are being created, what I'm going to do with my piece of paper, and just like you can see on the screen is I am going to put my angle detector in line with one of my edges, like this. And then with the second piece of card on the detector. I'm going to move it. So it's going to turn and I'm going to make sure it's in line with my other edge. Let me try again. Okay, fantastic. So here I can see that it has created an angle in the corner. And you can see that as well with my red and blue angle detector. That it has created an angle in this top corner. Using your angle detector, or using what you know about angles, can you find how many angles are in this rectangle? So pause the video to have a look at that net. Fantastic, so to be able to explore this a little bit further, just like we did with my angle detector, I'm going to go to each of the corners and measure the turn that the lines take. And I can see there's another angle at the top. I can see there's another angle in the corner there. And I can see that that is another angle in the corner there. So in my rectangle, I could see four different angles. Could you explore this a little bit further? What I'd like you to do is either get a piece of paper or use your exercise book. And can you find how many angles are inside these two objects? Pause the video to complete this activity. Thank you year three, welcome back. I really hope you've managed to explore those angles. We can have a little look at this together. So my paper was in the same shape as my example. So if I held up my angle detector to the screen, I could have tried to work out how many different angles there were in the corners. And I should have found out that there were four different angles. And my exercise book is exactly the same shape. So again, holding up my angle detector to measure the turn. Here's one line, it turns into this line and the space between is my angle. So both of those 2-D shapes had four angles inside them. Let's have a look at some other shapes. So using your angle protector, if you've got one. if you don't have one, you might just use your finger to point out the screen. You might even use your fingers to make a little angle detector. Can you find how many angles are inside the shape? If you want to, you could use your ruler and draw this pentagon and start to represent our angles as well. So, pause the video to find the angles inside this shape. Brilliant year three, let's have a look on this one together. I'm hoping you are all enjoying using your angle detector. Or if not like I said, using your fingers or even pointing to try and find those angles. So, if I have a look at my pentagon, I can see that I have one, I follow the line down. Oh, there's a corner. It turns, that's the space between, so two. And it turns again onto another line. So angle three, there's space between. Keep going round, another corner. And it turns, so the space between four and five. My pentagon has five angles inside it. And if you did draw it, you well remembered that we represent some of our angles, either by drawing a semicircle inside or squaring gets off. That learning will be coming to you tomorrow and the day after to represent our angles. I've noticed something really special. Have you? I have a pentagon here. How many sides does a pentagon have? How many angles are inside this pentagon? Have a look at the screen. Count the sides. How many sides does a Pentagon have? Shout it out. Fantastic, it has five edges. Five sides. How many angles did it have inside? Shout it out. Fantastic, it had five angles inside. It has the same number of angles as the same number of sides. Do you think this will be the case for every 2-D shape? Let's explore that. So, here I have an arrow. Again, you might just want to hold up your angle detector to the screen, or you may want to draw using your pen and your ruler, this arrow to represent your angles. But how many angles can you find inside this shape? Pause the video now. Fantastic year three. So let's explore this one together. Can you shout out how many angles you found inside the shape? That was very interesting. I heard two different answers there mostly. I heard the answers five and seven. But I think we should explore and see which one is correct. So, using my angle detector, I'm going to find the corners and measure that turn. And I'm going to see how many angles I can find. So let's see. Here is my arrow again. So, if I follow it round, I've got my line here and it turns. So I've got one angle. And the line again, it turns the space between, two angles. And again, the corner here, three, four, and five. So if you said five. Actually if I look a bit closer, I think I can see some more angle. Shall we check? Yes, I thought you might want to check a little bit further. So from here, if I follow my line around here. Here is a corner. But it's a slightly different corner because the angle is very open. So, these two lines still intersect and still meet. So I think there's an angle on the inside here. And if I follow it round the arrow head. Again, the line here intersects with the other edge to create an open angle. So, if we this again correctly. Can we see there that I actually have two other angles inside these shapes? They're just more open. They're greater in size than my other angles. So if I check how many angles have. I got one, two, three, four, five, six, seven. The arrow had seven angles inside it. Could I have checked that? What was the rule with the pentagon? How many sides did the pentagon have? Five. How many angles did it have inside? Five. I can check here. Does my arrow have seven sides like it has seven angles? Count how many edges my arrow has. Count with me. So one, two, three, four, five, six, seven. My arrow has seven sides and it has seven angles inside. So does this mean that's the same for every shape? You're going to explore this a little bit further in your independent activity. So, what I would like you to do now is identify the angles inside our 2-D shapes in our independent main activity. So, you will need your paper and your pen and your pencil. I would like you to copy out the table if you can, and start to notice any patterns. When you are ready, come back to this video and we'll check through our answers. So pause the video now. Great job year three. You're doing such amazing learning today. Let's have a look at some of our answers. So, if I have a look at the shape A, which was a parallelogram, I can see that there are four vertices. Because each time my lines intersect, they turn creating my angles. So, it had four angles and it also has four sides. Let me have a look at B, which was our hexagon. Fantastic, again it had six sides and six angles. Every time the lines meet and turn it creates an angle. Again, C was an irregular hexagon. So if we count the number of angles inside, again, we had six angles and it has six sides. And the star was a very tricky one. I tried to trick you out here 'cause at the tips of our star, we can see some small angles each time our two lines join into set, they create that space between. But did you get the more open angles in the centre of the shape? So, if we count the number of sides, our star had 10 sides and 10 angles inside. So, what do we think? Is there a rule there? Fantastic, if you said however many sides there are, is the same number of angles inside then you are correct. Let's explore part B a little bit more. So part B, our first question said, look at the table you have just completed. What do you notice? Are there and in patterns and explain? So hopefully you will have written a little sentence to explain what patterns you noticed. So we could have said the number of sides on a 2-D shape will be equal to the number of angles inside the 2-D shape. For example, a square has four sides and four angles inside. So, remembering the number of sides also represents the number of angles inside that shape. And C, a reasoning question. Do you agree or disagree with Danielle's statement? My shape has four angles inside. It must be a square. Can you shout to the screen for me? Did you gree or disagree? Three, two, one. Thank you year three all joining and let's explore this one together. So, my shape has four angles. So if go back to that rule. If it's got four angles inside, then it must have four edges, four sides. So here's my square that Danielle was talking about. Yes, it does have four edges as well. But is a square the only shape with four edges or sides? Can you shout out any other shapes you know that have four sides. Three, two, one. Wow, there were so many different shapes. So we could have drawn some different four-sided shapes with four angles to check through answers. So, a rectangle also has four sides and it has four different angles. Well done. So we have our trapezium here, which also has four sides and four angles inside. And you might have also said our parallelogram. Again, it has four sides and four angles inside. So, if you shouted disagree then you got the correct answer. Her shape, didn't have to be a square 'cause we've proved it by saying it could have been any of these four shapes. Well done. So, we're almost finished with today's learning year three. So what I would like you to do to complete this lesson is to finish and complete your final knowledge quiz to prove what you have done or learnt in today's lesson. So pause the video to complete this now. Well done year three. And that's it for today's lesson. So a big well done and thank you from me. You should now be more confident and able to identify angles inside a 2-D shape. And we'll see you back here tomorrow to explore this even further, where we're going to start to learn that there are different types of angles. So goodbye from me, bye bye.

To identify angles inside 2D shapes

To identify angles inside 2D shapes

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UnitMaths / Angles and shape

Maths