Lesson video

Hi there.

My name is Miss Darwish and for today's Maths lesson, we're going to be looking at a type of transformation called Reflection.

So before we get started with the lesson, if you can just take yourself to a nice quiet place, ready to start.

So if the agenda for today's lesson is first of all, we're going to be looking at some reflections what reflections mean and what they are.

And then we're going to be looking at some missing lines of reflection and then reflecting some shapes.

And then at the end of course, there will be a quiz for you to complete on today's lesson.

So let's get started.

Okay, you're going to need the following three things, a pencil, something to write on and then a ruler.

So if you want to go and grab those things, we can start the lesson.

Okay.

Transformations.

So one way that we can transform a shape is to translate it.

So you can see in the image, the only thing that's different apart from the colour of course about the image, the size is the same.

Everything's the same, but the image has been translated.

Okay.

Now another way that we can transform a shape is to reflect it.

And that's what we're going to be looking at today.

So Reflection.

You can see an example in the image of swan looking at its reflection.

So when an image is flipped across a line of reflection, that's called a reflection.

So another way for saying reflection is by using the word flip.

When you flip a shape over, you are reflecting it.

Okay.

We look an example, we have got the mirror line, or we can call it the line of reflection, and then we've got a triangle and we want to reflect this triangle and it would look like this.

So that's the original, this is what happens when we reflect it.

Now, of course a triangle has how many vertices? Three vertices.

Well done.

So if we count from each of the three vertices and count how many squares until it reaches that line of reflection.

So you can see from the arrows, the one at the top, we've got four squares.

Can you see that? That means when we reflect the shape, the same point also has to be four squares away from the line of reflection.

And then one of the, cause we've got three vertices, the one at the bottom is two squares away.

That means it also has to be two squares away when we reflect the shape, cause it's a reflection.

It's exactly the same, but on the other side.

Okay.

let's have a look at reflecting this shape.

Where do you think it would go? So of course this is a rectangle.

A rectangle has four vertices.

So you might want to count how many squares until we get to the line of reflection.

So where do you think the shape would be reflected? Should we have a look together? Okay, well then if you got that right.

Why would it go there? So we are counting how many squares away, from the line of reflection and we make sure exactly the same happens on the other side of the line of reflection.

Okay, now what's the same and what's different? We've been looking at reflecting shapes on a vertical line, but we could also look at a horizontal line.

And later on in the lesson, you'll realise that lines of reflection don't have to be vertical or horizontal.

They could also be diagonal, but we'll look at that later on in the lesson.

So here is a horizontal line of reflection.

Where do you think the shape would go? So exactly the same as we would do, if our line of reflection was vertical, we still count, choose a one of the four vertices and count how many squares until we get to that line.

Okay, where do you think the shape will go? Did you get it right, well done if you've got it right.

And again why? So you can count how many squares away from the line.

Well done.

Okay.

We've got different shape.

The shape has got lots of vertices, so you can choose a few and reflect then remember to count each time.

And when you're ready in six, five, four, three, two, one, did you get it right? So look at the original and look at the reflected line.

Now, is this correct? So this is what I asked you to reflect.

Now, is this correct? I don't think it's correct, do you? So if you were worried for a second, cause you thought you got it wrong, don't worry because I don't think it's correct, but I want you to tell me why is this not correct? Why is it not correct? Okay.

When we count we're to choose from any of the vertices and we count how many spaces until we reach that mirror line or line of reflection, it is not the same on the other side.

So I can see for an example, there's three squares and on the other side there's only two.

That is definitely not correct.

Let's have another look.

Is this now correct? What do you think? Yes, now why? I agree, I think this is now correct.

And hopefully that was your original answer again.

If we're counting exactly how many squares away from that mirror line or line of reflection, it is the same on the other side.

This is now correct.

Okay.

Now let's have a look at reflecting another shape.

So again, it's always easier.

I find it easier when I reflect the shape, instead of trying to figure out where the shape goes.

I just choose, I look at where the vertices are and then I'll move one at a time.

So we can see the original.

But I want you to think why is this not correct? Look at each of the points and where they are.

So the easiest way that I find to reflect images, first of all I need to point out where the vertices are.

So I have done that in colours, using colours.

Now, if you look at the blue one, so the blue point, is it the same distance from the mirror line as the other, as the reflective blue point? It's not.

And what about the black and the purple then or either.

That's why it's not correct.

So for example, the blue and the black are only one square away from the mirror line, but when they reflect it, there's a lot more definitely not correct.

Now, is it correct? Okay, we look at each points again and we look at the blue point.

So we look at all three vertices and the blue is one square away.

So it's one square away when we reflect it, the purple is four away.

So on the other side, it's also four away and the black is one away.

So it's one away on the other side, well done.

Okay.

Now have a look at this shape.

So I've marked the four vertices for you.

Where do you think they'd go? Play with your finger to each of the four vertices so when we reflect it, if we were to reflect the shape, what would it look like? Okay let's have a look together.

Did you get that one right? Now the black one.

Did you get that right? Good.

And as well notice how the distance from the purple and the black both vertices it doesn't change.

It stays the same.

Remember when we transform shapes the actual size of the shape, it doesn't get bigger.

It doesn't get smaller.

The shape stays the same when we transform.

It's just matter of we translating it or of we reflecting it.

Okay.

And then the green one.

And then when once you hit the blue one guys, quit.

Okay, well done.

Once we've got all of the vertices, then it's safe to take out your ruler and your pencil and then join these points together.

Okay.

Now, remember at the start of the lesson I said to you, a mirror line or a line of reflection it can be horizontal, it can be vertical, and it can be diagonal as well.

So this is an example of a diagonal line of reflection or a diagonal mirror line.

So we've got our shape, and we've got the line of reflection.

And what's the first thing we do? What's the first thing I like to do, is mark out the vertices.

well done if you said that.

So, now it just gets a bit easier for us.

Now, we are still going to be counting, how many squares away from the line, but we are doing some diagonal counts.

Okay, so we're not counting across, we're not counting down, we're counting diagonal counts.

So we need to have a look, at the purple.

So can you see the purple point? It is one and a half squares away.

Can you see that? So on the other side when we reflect the shape, it also has to be, one and a half squares away like in the example.

Because we did diagonal counts because our line of reflection is diagonal.

Okay.

And then that's where the black one would go.

How many squares away Is it? One, and then the rest.

Have a look at the blue one, how many squares away diagonal counts, so we're doing diagonal counts is the blue one.

Three, so it's also three on the other side.

Okay, is that an easy way? I find this method easy for me just to mark all the vertices first, and then I take one at a time and I do some diagonal counts, and then I plot them and then when , I can then draw, join the lines together, join the points together with my ruler and pencil.

Okay, Now, when we reflect shapes, so you can see the original I've labelled the vertices you've got A, B, C, D, and E.

Now, A, when it's being reflected, it becomes A dash.

B when it's being reflected becomes B dash.

C is the original when we reflect it, so the same point that's being reflected, so what's called C in the original, and when the same points being reflected It's called C dash.

D is the original again, D dash and so on.

And that's usually what we do in math, so I can make it easier, rather than colour coding everything coloured all the time, we just use a notation so, for example if there's X, a point X, when we reflect it would be called X dash.

Okay, hopefully that was clear.

So now I would like you to, pause the video and have a go at the independent task, just try your best, and once you've finished it, then come back and we will go through the answers together.

Good luck.

Okay welcome back, hopefully you found those okay not too tricky.

Should we go through the answers together now? Let's have a look.

So for your independent task, you asked to reflect the triangle and label the new vertices.

So we had a line of reflection which was diagonal, and we have the three vertices A, B, and C.

So, what happens when we reflect A, B and C? And don't forget hopefully you remember to label it as well.

So, A is one diagonal space, one diagonal square from the mirror line, so A dash is also one diagonal square away from the mirror line.

What about B? Two diagonal squares from the mirror lines, so B dash is also two diagnose squares been the mirror line.

What about C? Three diagonal squares from the mirror line, so C dash is also three diagonal squares from the mirror line.

So well done if you got those correct.

Okay, well done on all the learning you've done today.

If you would like to share your work with Oak National, then please ask your parent or your carer to share your work for you on Twitter and ask them to tag @OakNational and #LearnwithOak.

I would love to see the learning that you did today.

Now it is time for you to go and complete your quiz on today's lesson, I just want to say, a massive well done on all the brilliant learning that you have done today on reflecting shapes, so well done and good luck with the quiz.