Shape and symmetry: To identify acute and obtuse angles

Key Stage 2

Maths

2-D Shape and Symmetry

How many right angles does this shape contain?

Which of these shapes contains at least 1 right angle?

Estimate this angle. Which guess is closest?

﻿So you're going to need a pencil, a ruler and if you have it, and I've made a little bit of a revised version, 'cause the last one was huge, your little thingamabob, whatchamacallit angle duda what's it. If you have that, brilliant, that might be useful for you today. You'll need some paper, something to write on and somewhere quiet with no distractions. So don't just go sit in a room and try and grow your hair super fast. Let's make sure that we are listening and ready to learn. So, our agenda then, we've done our knowledge quiz. We're going to move on in a moment to our key learning and vocabulary and then some speed times tables, yeah! Then we're going to recap on angles with a focus on acute and obtuse. Then our main activity, so we're going to create angles to fit a certain criteria. And then a final knowledge quiz to see what you've remembered from today's session. So if you remember every week so far, I've been saying, let's get on top of our times tables, let's be speedy with them. I've made it a bigger test today. A bigger challenge for you. There are more, so be prepared. So our key learning then, is to identify acute and obtuse angles and here is our key vocabulary: angle, degree, acute, obtuse, right angle, order, compare, 90 degrees, 180 degrees. Perfect, all right. So as promised, here is our mega tables challenge. Give it a go. See how many you get right in a short amount of time. As soon as you've finished, write down your time. Hopefully, we'll get quicker each practise. So give it a go and I will see you very shortly on the other side when you have used all of your brilliant mathematical times table skills, which I know you all have. So without further ado, here's your challenge. How was that for you then? Did you do all right? I'm sure you did. So let's take a look at those answers. Now I'll tell you that I started with the ones I find simpler. So I did my tens first. I did my twos first. I did some fives because they're always the ones I can base everything else around. So here are the answers. Interestingly as well, I don't know if you've ever thought of it this way, but with your times tables, you actually only need to learn half of them. Because if I learnt, for example, two times seven, then I know seven times two. That's my seven times table and my two times table done. I know it. So you only really, technically need to learn half, because then you can just flip it and know the rest. So if you think of it that way, learning your times table seems less of a task. You still need to be able to answer questions quickly, but there are ways of getting around it and knowing how to calculate them really easily and remember them really easily. So any tricks you've got, share them with people at home. If you've got ways of doing it, share it. It's really helpful. So let's move on. Let's look at today. Oh, look at this. How have we seen this before? Yes, I think we have, but I do think it's worth just recapping on what an angle is. So remember an angle is where two lines meet each other and the space where they meet is then our angle. So we have our acute angles. We have our right angles, our obtuse angles, and our reflex angles, okay. Pretty straightforward, easy to remember. So well done. So really quickly then can you match again? We've done this, but I've jumbled it up a little more. Can you match the type of angle to the definition and then also to the name? Okay. So we've got the name of the angle, the definition of the angle, and then an example. Can you match them and get them just right? Now remember, I gave you little pointers on how to remember what each type of angle was. So I told you about the acute angle and the obtuse angle. And that right angle is right on a particular measurement. So I've given you those examples that should, in theory, help. Five seconds more. And three, two, one, here he comes. So, our right angle, let's say it together just to remember them, okay. A right angle is exactly 90 degrees. How big is a right angle? Exactly 90 degrees. An acute angle is less than 90 degrees. An acute angle is? Brilliant. And an obtuse angle is more than 90 degrees, but less than a 180 degrees. What's an obtuse angle? Amazing. Fantastic work, well remembered. Keep it up here, that's going to help you with everything else we do with angles and shape. So, just a reminder then, when we use our protractor to measure it, an acute angle is less than 90 degrees. An obtuse angle is more than 90 but less than a 180. So, sort the angles here into right angles, acute and obtuse. Now the right angles should be really easy to spot. They're marked off slightly differently. The rest of them, not always as easy, so just be careful with it. Another logical way of thinking of it, is if it's smaller than a right angle, it's acute. If it's bigger than a right angle, it's, yeah, obtuse. So, smaller than a right angle is acute. Bigger than a right angle, obtuse. Remembering that then, you're going to put the labels, uh, the names of each letter-- Sorry, the names of each angle, into your table, okay. So, when you see, for example, angle B and you think, okay, that's a right angle, I'll put it in the right angle section. The table you've got looks something like this. Three sections and just some sentences at the bottom that might be helpful for you to help you remember A right angle measures, mph. An acute angle is more than, um and less than, um. Now I haven't told you what an acute angle is more than. So how can you be able to figure this out? We know what it's less than. And then finally, an obtuse angle is more than um and less than hmm. So, looking back at those angles, can you sort them into acute, right angle and obtuse angle? Put them into this table. Just remember very clearly, the rules that we've stated. Okay, we've said what each of those type of angle is. So your task time starts now. Hi, welcome back. So should we see how you did? Let's. So our angles were all here. The right angle should have been super easy to spot. They looked different to all the rest of them and this is where we should have placed them all. So C and D were the only two that were right angles and they really stood out because their corners were marked just like this, with that little square to show that it's a right angle. When it's marked off like that, we know that it's a right angle, okay. So a right angle measures, you got it, 90 degrees. So hopefully you've had that down at the bottom. An acute angle is more than, now I didn't tell you what it was more than. I told you what it was less than. We all knew that it was less than 90 degrees, but you should have known that it was more than zero degrees. Cause it it's zero degrees, there's no measurement there at all. And obtuse angle is more than 90 degrees and less than a 180. Okay? So look over the answers. This is where you should have placed each of those angles. Well done. So moving ahead, have a look here now. We've seen images of them, but can you figure out where they would fit just based on the numbers? Right, now I've given you the criteria. I've told you what each of those are at the top. The example is there, right there. Tells you the measurements. So the measurements at the bottom, can you sort them and put them into the right places? Give that a go. Remember. Oh, do you know what, let's take it away. An acute angle is less than, yep. An obtuse angle is more than? But less than? Guys, you know this. So let's not spend any more time there. Can you match them? You should have three for each 10 seconds. Three, two, one. And here we go. So how did I know that six degrees, 20 degrees in 64 degrees were all acute angles? Because they were all less than 90. And for the obtuse angles, I knew they're obtuse because they all lay between 90 degrees and 180 degrees. So, big thumbs up for getting that correct. Well done. So, here is our main activity today. We're going to be looking at drawing angles based on certain criteria. Now criteria are basically another way of saying, I guess it's like rules. I give you a rule of what it should look like and then you try and draw it that way. So for example, if I said draw a blue dog, the two criteria are that it should be a dog and it should be blue. You have to tick off both of those boxes say, yes, it's a dog, correct? Yes, it's blue, tick. Well, we're going to be a little bit more technical than looking at blue dogs. Looking over the types of angles. So for example, the first question says, and I've given you some square paper there to do it on or if you're doing it at home, that's fine on a paper. That's also fine. Draw two different acute angles, using a ruler to stay neat. So there are a few criteria there. One is that you need to draw two angles. Another one is that they have to be different. A third criteria is that they have to be acute. And a fourth criteria is that you use a ruler. Please use a ruler. Wibbly wobbly spaghetti lines ain't cutting it for me. They don't make neat angles. So for each of those and we'll do it a step at a time, we'll do four at a time. For each of those, you're going to try and fulfil the criteria. Follow the rules for each one and draw what I've asked you to draw. Okay. Don't worry too much about the number of degrees in each angle. I just want them to be either acute or obtuse. I'm might even throw in some right angles. So give it a go. Have a look at those and see what you can come up with, okay. But I will just say again, you can't do neat angles without using a ruler, okay. You must use a ruler. That's really important. So give it a real good go and then I'm going to come back with a couple of examples, okay. So, good luck. Back in three, two, one, here we are then. So let's have a look at that first section, shall we? The first one, I asked you to draw two different acute angles and using a ruler to stay neat. So I've done my couple here and yes, they are different because they are slightly facing different directions. I'll accept that today. And they are acute because they are less than 90 degrees and I've drawn two of them. Here I've asked you to draw two different obtuse angles. So they need to be, yep, bigger than 90 and less than 180. Well done. So I've got those in here as well. So if we look really carefully there, we can see that I've got my two different obtuse angles. Then I had to draw a triangle with one obtuse angle. Here's my triangle. I know it's a triangle because it's got three sides. Tell me, spot the obtuse angle? Yeah, it's right here. Here's my obtuse angle. And then I had to draw a triangle that had one right angle. Here's my right angle. So that must be a triangle with a right angle, okay. Really well done. So, how do you think that was? Should we challenge you with the next one? Okay, so here's the next bit I want you to have a look at All right? First one is, draw a quadrilateral with two acute angles. A quadrilateral has how many sides? Quad, quarter, quad, quadrant. Yeah, four sides. So you're going to draw a four sided shape with two acute angles. Then a four sided shape with two right angles. Then a pentagon with one acute angle. Pentagon, remember? Yup, five sides. Pentagon with a total of three acute angles. So each time, we're looking at finding the criteria, following the rules and then seeing what we can come up with. So, are you ready? You're going to pause again and give it a go. I'm coming back in three, two, one, and we are back. How was that then? Shall we have a look at some answers? Now for this, there are several different ways you could do because each shape, you could draw it slightly differently. So just because I've drawn a specific one, doesn't mean that's the only correct answer. These are just my versions. And here they are. I know this first one is a quadrilateral because I've got my four sides, look, my one, two, three, and four. And I needed two acute angles. Oh look, this is less than 90 degrees and so is this one. And if you can remember what we call that kind of shape? I'll give you a clue, it's the one that I have to say slowly, because there are too many L's in it. Yeah, you got it. It is the parallelogram. So I have to go so slow on that one. Parallelogram, parallelogram. Oh, that was pretty fast. All right. I will look at the next one. A quadrilateral with two right angles. Let's just check it's a quadrilateral. One, two, three, four sides, is that right? Yeah, quadrilateral, four sides. And here are my two right angles, one, two. Here is not a right angle, so good, check. And this is an acute angle, check. Brilliant. Now I have to draw my pentagon with only one acute angle. So only one angle less than 90 degrees and a pentagon, remember, has five sides. Let's just check the sides first, one, two, three, four, five. Brilliant. And here's my one acute angle. This time a five-sided shape, a pentagon, with three acute angles. Let's just take one, two, three, four, five sides and my three acute angles. I've done it. I fulfilled the criteria. How did you do? You might have even come up with some things a lot more fancy than mine. So hopefully, you managed just brilliantly. So here is your challenge for today. I'm going to ask you to pick three of the flags and write sentences to describe the patterns on them. Now, when you do pick them, I would love it if you could very, very clearly, describe what you can see in terms of angles. So for example, the Chilli flag is really good to talk about different types of angles, as is the Brazilian flag or the flag of Guyana or Suriname. Great things there. Anything with a star gives you plenty to talk about. You might want to talk about how many obtuse angles there are. You might want to mention how many acute angles there are. You might want to mention how many right angles. We've done all of those things, so can you think of some really good descriptions? That's your key takeaway for today. That's the key thing I'm asking you to work on. That is your challenge. So best of luck with that, guys and very well done.

Shape and symmetry: To identify acute and obtuse angles

Shape and symmetry: To identify acute and obtuse angles

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UnitMaths / 2-D Shape and Symmetry

Maths