Shape and symmetry: To identify right angles

Key Stage 2

Maths

2-D Shape and Symmetry

What kind of angle is less than or equal to 45 degrees?

Which of these shapes can NEVER have a right angle?

What kind of angle is more than 90° and less than 180°

﻿I hope everybody is well, hope you are happy and healthy and ready to learn. So let's get straight on shall we? So for today's lesson you're going to need your usual, your pencil, your ruler. And today you're also going to need another piece of paper. So you're going to need something a little like this. So just a regular rectangular piece of paper. It can be this size, it can be this size. It doesn't really matter. As long as it's got nice straight edges, that will be much more helpful than anything. Okay? You're also going to need your paper or books that you've got from school and somewhere quiet with no distraction. So put that Lego away and don't get building with it. So our agenda for today's lesson, we've done our knowledge quiz. We're going to move on to talking about our key learning of vocabulary in a minute, and then a number trees one. We did number trees last few sessions ago, and I think it was quite enjoyable. I certainly enjoyed putting it together. The slide look real nice and pretty and I think you guys, from what I've heard back on social media, you've really enjoyed it too. So let's have another one of those. And then we're going to recap on what angles are, the focus angles for our next few sessions and then today's main featured angle, the angle of the day, the right angle. And then we're going to move on to finding right angles, using our special bit of equipment that we'll be developing and also then our final knowledge quiz. So our key learning today is to identify right angles. And our key vocabulary is angle, degree, acute, obtuse, right angle, order, compare, a really important one here for right angles, 90 degrees. Brilliant. So shall we move ahead? Let's do that. So here is our warmup, our to start activity to get our brains really working. Now remember, I'll talk you through really briefly how we do this on a number tree, the two numbers below add together to give the number above. So six add three gives me nine. One add six gives me seven and so on. And then I would add these two together to give me this and so on. So let's have a look at this one. Now if I'm not doing addition, and I can't here because I have one of my digits missing, so I can't do the division part yet, but I can do the-- Addition sorry, not division. I can do the opposite though of addition. The inverse, which is? Yep, subtraction. So if I subtract the one from the seven that will give me what should go here. So seven subtract one. Seven, takeaway one is? Yeah. And then I can do six, I can do seven, and so on and work my way up until I get ding, ding, ding, to my top number. So have a look at the these. They're trickier this time, last time round I left you with more numbers. This time taking quite a few more away from you. Don't forget if you can't use addition, not division, I don't know why I was saying that before. If you can't use addition, you use the inverse, which is subtraction to work your way from the bottom of the tree to the top. And in some cases you might have to work backwards as well and go down slightly. So give it a go, see how you do and come back when you're ready. And I think we're ready to rejoin each other. So shall we see how we did with those answers? So casting your eyes over. I had my two and my 13 which gave me 15. I needed 15 add gave me 20, and then I could work my way this way. Five subtract two gave me three. Adding them up, working my way until I get to 30 at the top. With this one I started here. This is where I started. I found that one easier. So I did 13 add 17 which gave me the 30, took that away from 55 to give me the 25 and worked backwards. And I did something similar here. I needed to know what number I was ending with as well. So I did my seven add the 10 to give me the 17 and so on. Hopefully we did all right with that. I'm sure we did. So let's move ahead to our main bit of recap. So let's recap on what an angle actually is. So an angle, remember, is when two lines, in any kind of way, meet each other at a point. Now, angles are measured in degrees. Not like in temperature, but it's still represented using the same symbol. And if you remember I said to you that this circle, the floating circle there isn't a zero. It's because a full circle, a full turn, relates directly to degrees. Okay? And there are four main types of angle. This last one here we're not focusing in on at the moment. And if you remember, I've shown you them, ranging from smallest type of angle to largest. So let's just recap on those names, say them with me, acute angle, right angle, obtuse angle, and reflex angle. And if you remember yesterday, you had that little bit of equipment that we used to help you sort of estimate the size of angles just by moving it around a little bit, a bit like an elbow. Helps you to estimate the size. Today we'll be looking at using another sneaky little piece of equipment as well. So just to recap then, an acute angle is anything less than 90 degrees, okay? Acute, small, cute like a mouse. Remember that dreadful picture I drew in the last session? Hopefully that's stuck into your mind. It's probably stuck into your mind for all the wrong reasons because it was such a dreadful picture, but it might be useful that it's now lodged in there. The next type of angle was a right angle. And this is our focus one for today and our right angle is right on the mark for 90 degrees. And we represent that instead of a curve in the corner, we represent it with a squared corner. 90 degrees is a right angle. And an obtuse angle is larger than 90 degrees. As we can see here, this is 90 degrees, but our obtuse angle has gone past the 90 degrees but it's less than 180. 180 degrees is certainly a straight angle or a straight line. So let's make a second type of angle estimator, and I'll show you how to do that now. So you're going to need your piece of paper. Here I go. Tadaa! Something like this. Now on your piece of paper you're going to need to do some folding. Whoops. So if we look really carefully I'm taking the top part and I'm folding it down to meet the edge. And if I turn it round I've drawn a little dotty line to show you. So the top part I'm folding it down and then very neatly lining it up with that edge. Okay? So now I've got something that looks, oop! I'll get this camera thing right in a minute Something that looks a bit like that. Bit like a sailing boat, I guess. So I've brought, let me show you once more, the corner at the top. The whole of that side is folded down diagonally to meet the edge of my paper. Oh, that's it. You've done it, simple as that. So now that I folded that I'm going to give it a real sharp crease, that helps. It's a really sharp crease. This is what I need. And if I show you really quickly, I've then just marked off where all the different angles are that we can use. And the one that we are interested in are these two at the bottom. Here we've got 90 degrees, here we've got 90 degrees. At the top we've got half of that 90 degrees. This is 45 degrees, okay? And here, whoops, we have the 90 degrees add the 45 degrees. This is 135 degrees. Sneaky stuff right? But the two that we're most interested in are this one and also this one. Okay. Now that was hard for me. The folding part was not hard, but lining everything up on the camera? Ugh. I don't think I did the most professional job of that, but all I can then do with that. Let me see if I can find a little book I can show you with. So for example, if I just use a book here and I line this up with a corner. So I'm going to line it with that corner, I can see the corner of my book fits in perfectly. It's 90 degrees, okay? If I were to look at something else, let's have a look. Oh, let's just compare it to this other piece of paper here. So if I line up my 90 degrees with that corner. Oh no, I can see there's some left. So this isn't a right angle. It's bigger. Okay? So it's a really useful little piece of silly equipment that you can use to help you line things up. All right? So hopefully that's going to be useful for you. So if you didn't know how to make an angle estimator, you just got one. Now that is a quite an accurate measurer. It only is accurate though if your piece of paper that you start with is really straight on the edges, Okay, sharp folds. So, enough of that dithering around. Surely it's not going to take you as long as it just took me. I just could not get that lining up right. So just to recap finally one more time. A right-angle then is right on the mark, it is 90 degrees, the corner of a square, the corner of an oblong, an L. A capital L kind of shape. That is a right angle. So, using that piece of equipment that you just made, you've got a selection, A, B, C, D, E, F, G, H, and I. All of those are different angles, but not all of those angles are 90 degrees. Only some of those angles are 90 degrees. What's another name for 90 degrees? Yeah, a right angle! So only some of them are right angles. Now you need to try and spot them. Now you're going to get a table that you need to fill in, and your table looks like this. You're going to tick under the letter if it's a right angle and cross where it's not a right angle. So for example, if I thought letter A, if I thought angle A was a right angle, I'm going to tick it. If I think it's not a right angle I'm also going to cross it underneath. Is it possible for me to do this? I think B is a right angle. I think B is not a right angle. Uh-uh. It's either a right angle or it's not. So I can't have two ticks underneath a letter. I will need a tick and a cross. Okay? So that's your task, matching up which you think are the right angles, ticking them off, okay? Find the right and tick it. And I'll see you when you're ready. And back in three, two, one, and let's see how we did. Let's check over those answers shall we? So there were only three that I thought were right angles and they were E, G, and I. Now remember, I said that some of them would have been quite close. And so what I would have done would have been to have used the corner of that little piece of equipment we made. Okay? So let's just come straight back and have a little look at those. And you can see that if I look at E, that clearly fits into the corner of the square. Our little angle estimator, our measure would work. And so I'm going to just convert that like this so we've got the correct showing of a right angle. So E definitely was, G definitely was. And so was I. Now F and B were super super close, but if you look really carefully you can see that B is just smaller and the same with F, okay? Just, just smaller. And again, remember it doesn't mean that the bigger the lines, the bigger the angle. Try and remember that really carefully. It doesn't mean the bigger the lines, the bigger the angle. That's not how it works. So hopefully, and we'll just give you a second to have a look at those answers again. Hopefully you did really well on that. Let's see. I just gave you a little reminder there to say, remember a right angle is just like the corner of a square. Okay. So here is your main task for today. Now you've got a whole series of shapes there. All you're doing is going on a little bit of a hunt. You're not going on a bear hunt, you're going on a hunt for right angles. So have a look over those shapes and when you find the right angle, mark it off, just like we did here, okay? Now, when I come back to the answers, I'm not going to have marked them all, but we will look at where the majority of them are. So for example, going to give you one more freebie. This is another right angle here. So I'm just going to go [Humming] to mark it off. Wherever I see a right angle I'm going to mark it off like that, okay? Give it a real good go. It's quite a nice little bit of investigation here so enjoy it. Use your little tool that you made. If you need to make a smaller version, do that. It doesn't have to be that huge piece that I've just shown you. Sometimes just using a post-it note is perfect for it as well, okay? So give it a go, find those right angles and mark them off. But we're looking for right angles on the inside of the shape. So for example, if we look here at this one, I don't mean this bit here. That's clearly a right angle, but it's on the outside. I'm looking for what we call an interior right angle. A right angle on the inside. And for some of them you might need to turn your head and tilt your head to see where they could lie. Best of luck! See you in a few minutes. So we're about to have a look at where some of those right angles lie. Hopefully you got them right. If you did miss some, put them in, it's fine to do that now. Put them in now and if you want to just make sure that you remember where they are and you have a different colour pencil, or a different colour pen, put them in with a different colour. So you can show the ones that you didn't spot first time. Okay? So let's have a look shall we? Here are some of them and I've not put them all in. I'm going to mark a few more in for you as we are here. So here you'd have had another and also here, because actually this is just an oblong that's had one corner cut out. Now this is a special type of triangle. It's called a right angle triangle. Can you guess why? Yeah, simple as that, right? It's got a right angle in it. So if it's a right angle in it, it's a right angle triangle. Straightforward hey? Now the next one, I couldn't find any right angles there. As far as I could see, all those angles were more than 90 degrees. So they were all? Yep, obtuse. Let's go down here next. We had one marked off and there's also another one above in this shape. Nope, I have obtuse angles. I have an acute angle here. Another acute, another acute, no right angles. And the same with this. Am I right to call that a diamond? Is that a diamond? Uh-uh. It is a rhombus. And in that rhombus, no right angles. No right angles here. None, and this one I have one there. I also have another one opposite. So inside I've got one, two, three, four, five, six, seven, eight. Greedy one there with a lot of right angles. None here. Nope, nope, nope. And of course I have yes, yes, yes, yes. And here as well. This last one reminds me of when we were looking at shape, but we were looking at area and it reminds me of a composite shape. A composite shape made up of a couple of smaller shapes squished together. Well done! Quite good fun looking at that. And if you want to challenge yourself even more, you could find an alphabet written out in block capitals and look for right angles in capital letters as well. That's quite good fun. I certainly spent quite a lot of time doing that the other day when I was putting off a lot of other things that I should have been doing, I thought let's investigate some maths. So moving ahead, here is your final challenge. Your key take away for today! How many right angles can you spot in this picture? When you find them, remember we marked them off with a small square, just like we've done before. So here's a freebie for you, I'm going to go to the top corner, go to the most obvious one and I'll mark it off like that. How many can you find? What might be quite nice is if you had this and someone else had it in front of them, you could challenge each other and see how many you could find in three minutes. See who finds the most. Best of luck. Give it a go! And let's move onto our final thing. Let's just really quickly take a look at some of the ones I'd spotted, excluding the freebie that I gave you at the top, which was you? Another one there, there, here, here, here. I was doing a lot of this to try and spot them. And I'm sure that you probably did as well. If you were unsure-- I'm back! Hopefully you used these to help you. The little angle doodie whatsit that we made. So well done!

Shape and symmetry: To identify right angles

Shape and symmetry: To identify right angles

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UnitMaths / 2-D Shape and Symmetry

Maths