Lesson video

Hi, I'm Miss Davis.

In this lesson we're going through reflecting objects in horizontal and vertical lines.

Let's start by looking at reflectional symmetry.

How many lines of symmetry does this Pentagon have? Well, it only has one.

If we fold this Pentagon in halves along this line, these halves will be identical.

This means it is the line of symmetry.

There is no other line on this shape that has this property.

How many lines of symmetry do these shapes have? Pause the video to complete your task and resume once you're finished.

The rectangle can be folded this way to give two equal parts.

It can also be folded this way.

So the rectangle has two lines of symmetry.

Let's look at the arrow.

This is the only line of symmetry that the arrow has.

If we're reflecting an image in a mirror line, both sides of it should be identical.

It then becomes a line of symmetry.

Let us reflect this shape in the mirror line.

You can see that both sides of the mirror line are identical.

Which diagram shows the correct reflection? It's shape c, both sides of the mirror line are identical.

Which image shows the correct reflection? It's shape c, as both sides of the mirror line are identical.

We're going to reflect this shape in the mirror line.

We're going to work with each vertex individually.

Let's start with the one on the left.

This vertex is two squares from the mirror line.

This means it's going to be two squares on the other side of the mirror line.

Next, let's look at the one on the right.

This is three squares from the mirror line.

So the same vertex will be three squares, the other side of the mirror line.

The two vertices in the centre on the mirror line.

So they will stay in the same place.

Finally, we need to join these points together.

We can say that both sides of the mirror line are identical.

We're going to now reflect this shape in the vertical mirror line.

Again, we're going to work with each vertex individually.

Let's start with the vertex on the right.

This vertex is five squares from the mirror line.

So five squares on the other side of the mirror line is where this point will be reflected to.

Let's go for the next one in.

This vertex is three squares from the mirror line.

So when reflected, it will be three squares on the other side.

These two vertices are on the mirror line.

So they will stay there.

Finally, we'll need to join together these vertices to give our reflected image.

You can see that both sides of the mirror line are identical.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

Make sure that both sides of the mirror line are identical.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers.

For the second question, which has got an onset of delta, you might have written arrowhead.

While this is technically correct, the correct mathematical word for this shape is delta.

Here are two questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers, make sure that your images on both sides of the mirror lines are identical.

Here are some questions for you to try.

Pause the video to complete your task and resume once you're finished.

Here are the answers, the image in each quadrant has one line of symmetry.

Plus we've got the two mirror lines.

This gives us a total of four lines of symmetry.

That's all for this lesson.

Thanks for watching.