REVIEW: An angle is formed when two lines meet

Understanding angles

Key Stage 2

Maths

Angles

﻿Hello everybody, my name is Mr. Kelsall and welcome to today's lesson on angles. Now, before we start, you will need a pen, a piece of paper or something to write on. You'll also need a paperclip or something to fasten together to your piece of paper. Please don't forget to try and find somewhere quiet around the house, somewhere where that you won't be disturbed. And also don't forget to remove any sort of distractions away. For example, put your phone on silence, or move it away completely. Now, when you're ready, pause the video and let's begin. So today's lesson is all to do with understanding angles. And the plan for today is we need to understand what is an angle? We also need to understand how to measure angles. After that there's an independent task, and finally, it's time for your quiz. As I mentioned, you'll need a pencil, piece of paper and a paperclip. But first we need to understand angles. So let's start, have a look around the room. Can you find any sort of angles? Have a look in the corner of your room. When the door opens that creates an angle, when you turn the page in a book that creates an angle. But we need to have a definition of what is an angle. So, an angle is formed when two lines meet. If you look at the three examples on the page, these pairs of lines meet to form an angle. However, if you look at these three examples, these pairs of lines do not meet to form angles. Take a moment, have a look at the examples, which pairs of lines form an angle? I'll give you five seconds. Hopefully, you're going to tell me the final angle and the first angle, are both angles because they have two lines that meet, whereas the middle one, the lines don't meet. Shapes also have angles too. So if you look at this triangle, there are three lines. And if you look in the top corner, the two lines meet to form angle. If you look into the two corners as well, both of these lines meet to form an angle. So take a moment, have a look at this rectangle. How many angles are there inside this rectangle? Five seconds. Fantastic, there are four angles inside this rectangle. By now I'm thinking a triangle has three sides, and it's got three internal angles. This rectangle has four sides, and it's got four internal angles. Lets have a look at the next shape. How many angles are inside the shape? Five seconds. There are five angles inside the shape. A five sided shape is a pentagon, and there are five angles inside the shape. Okay, now we get into some trickier shapes. Can you spot all of the angles inside the shape? Five seconds. I would hope that you've certainly spotted these five angles. However, if we count the shape it has one, two, three, four, five, six, seven sides. So I'm expecting seven angles, but I've only got five angles. If I look closer, they're actually two more angles, here. Now, these two angles are a little bit different than the other angles. The other angles all stopped and they're just small angles, acute angles. Whereas this angle turning right the way around to make what we call a reflex angle. We'll learn more about reflect angles later, but at the moment, we just need to be able to identify where an angle is. Okay, time to pause the video here. Here are four shapes, triangle, pentagon, a rectangle, and an octagon. Can you find the angles inside these shapes? There are a lot of angles inside these shapes. If you look at the triangle, there are three angles. The pentagon, a five sided shape, has five angles. A rectangle, a four sided shape, has four angles. And an octagon, an eight sided shape, has eight angles. Okay, now that we understand what an angle is, we also need to understand how to measure an angle. In a moment, I'm going to show you how to make your own angle makeup, your angle measurer. Once you've done that, use that to measure the angles which are coming up. So we are going to make our angle measurer. All you need is a little bit of paper. I'm using two bits of paper, green and yellow so that you can see it clearly, but it doesn't matter what colour the paper is or what size it is really. All you need is two equal pieces of paper. So I'm just going to fold it over and tear it. You can cut it if you've got the scissors. And once you've done that, pop a hole through both parts. A hole probably big enough for a paperclip and then just thread your paper clip through. And there you have an angle measurer. All it's used for is to work out how much turn an angle is made up of. So if you can place your measurer there and you're going to turn one part of it around and you'll see how big that turn is. So, as we know, an angle is an amount of turn between two different lines. And we can measure this using an angle measurer. I've made my angle measurer here. I didn't have a split pen, so I've just used a little bit of cable tie to pop it through there so I can turn my angle measurer. I'm going to hold one side and I can see that the amount of turn I need is just a little bit. It's just from there to there. However, when I look at this side, the amount of turn I need is much more. I've got to go all the way around to here. So I know that the first angle is smaller than the second angle. Or I could say the second angle is greater than the first angle. And that's because the second angle has more turn than the first angle. So the first angle has less turn than this second angle. Can you say that? This time, I have to turn my angle measurer around a little bit differently. I need to line up with one line here and I need to, to adjust until I've got my second line lined up and I can see the amount of turn for this one, is just a small amount of turn. With my second angle, again, I'm going to line up my baseline. Once I've got my baseline, I want to make sure I put it in the right place. I'll need to adjust it a little bit. Now I can see the amount of turn for this angle is much greater. So my angle maker has just come apart. If it comes apart and that's quite normal, just pop it back together. Now, when I'm doing this, I need to line up one line and then the other line, but it doesn't matter which way you line it up. I can line my green line on the first line and my yellow piece of paper on the second line. Or I can do it the other way around. I could line my green line up there and my second line, my yellow line, up there. Now, all I'm looking at is the amount of turn. So I can see this amount of turn, it almost goes around one quarter of the way, but not one quarter just under one quarter. And I put my second angle measurer on. And again, I'm looking at the amount of turn. So I know if I'm going from when the lines and the paper is together, I'm moving it around a little bit, to there. And that's gone much less than one turn, one quarter of a turn. So I know that the first angle is greater than the second angle. Or I could say the second angle is smaller than the first angle. Now that you've had an opportunity to use your angle measurer, we now need to see if we can take that knowledge and look at an angle and simply work out the size without actually using an angle measurer. On your screen, there are three angles. Which angle is the greatest? I want you to imaginary put your angle measure up on each of the angles and which angle turns the furthest? Okay, take a moment, pause the video. And then put the angle measurer on the screen and see if your answer was correct. Fantastic, you will have seen that third angle, is the largest angle. That's because the angle measurer turns the furthest. Again, see if you can imagine which angle is the biggest. Can you see it? So, this is a triangle. It has three sides and therefore three angles, which angle is the greatest? The top angle is the greatest, because it's got the most turn. Next question, we have a triangle, it's three sided shape, therefore has three internal angles. But this time, which angle is the smallest? Again it's the top angle, which is the smallest. This time there are four shapes. A triangle, a rectangle, a pentagon, and a square, which shape has the greatest angle? Pause the video and when you're ready, press play. A little bit tricky this question, because one shape has two angles which are quite a large angles. The Pentagon has the largest angles. Again, pause the video, which shape has the greatest angle? The arrow has the greatest angles. Okay, now it's time for your independent task. Have a look at the questions on the screen. There are four shapes. Question number one, how many angles are there in each shape? Can you find the greatest angle in each shape? And can you find the smallest angle in each shape? Okay, pause the video, press play when you're ready. Okay, and here are the answers. So the triangle has, both triangles have three angles. The Pentagon has five angles. And the trapezium, which is a quadrilateral, is a four sided shape, has four angles. You'll see that the circles show the greatest angles and the squares show the smallest angles. Hopefully you've managed to successfully complete that task. If you'd like to, please ask your parent or carer to share your work on Twitter tagging @OakNational and #LearnwithOak. Also, don't forget to complete the quiz. So, that brings us to the end of today's lesson. A really, really, really big well done on all the fantastic learning that you've achieved. Before you go perhaps quickly review all of your notes from today and decide what's the most important thing that you've learned. Well, all that's left for me to say is thank you, take care, enjoy the rest of your learning for today.

Understanding angles

Understanding angles

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UnitMaths / Angles

Maths