Lesson video

Hi, I'm Miss Davies, in this lesson, we're going to be looking at reflecting images in diagonal mirror lines.

We're reflecting this image in the mirror line that is shown.

Which diagram shows the correct reflection? It's A, you can see that both sides of the mirror line are identical.

Part B, although you could say that they are the same, it is not a true reflection.

If we look at the top side of the rectangle, the left hand side of the mirror line has got two squares and the right hand side has got four squares, so it is not a true reflection.

Let's have a go at performing this reflection.

Because our mirror line is diagonal, we need to count from our vertices diagonally.

We're going to work with each vertex in turn.

The two that are on the mirror line will stay where they are.

Let's start with the bottom vertex.

We can see there is one diagonal square from the mirror line, when reflected it will go one square the other side.

We can see that our dash lines meet our mirror line at a right angle.

Let's look at the next vertex, this is two diagonal squares from the mirror line, again, with that dash line meeting the mirror line at a right angle, it will then be two diagonal squares the other side of the mirror line.

Now, that we've got our four vertices, we can join them together.

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 you're not rushing with these questions, reflect each vertex individually in the mirror line and then join up these points.

Let's have a look at this example.

What is different about this question compared to the ones that we've already looked at? Well done if you noticed that on the previous questions, there's always been at least one vertex on the mirror line, in this question, there aren't any vertices that are on the mirror line.

We're going to answer this question in the same way, we're going to work with each vertex in turn.

If we start with the bottom right vertex, we can see that it is one diagonal square from the mirror line.

When reflected it will be one diagonal square the other side of the mirror line.

Next, we'll look at the bottom left vertex, this is two diagonal squares from the mirror line, when reflected it will be here.

Our final point is a little bit trickier as it isn't on an intersection of two lines.

We can see that it's about a third of a diagonal square from the mirror line, we would need to measure this distance with a ruler to make sure that is exactly the same on the other side.

Now, that we've got our three vertices reflected, we can join these together.

We can see that the images are identical on both sides of the mirror line.

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 you're reflecting each vertex individually so that you don't make any silly mistakes.

Here is a question for you to try, pause the video to complete your task and resume once you're finished.

Here is the answer.

Diagrams A and C have the same orientation in the reflections, this rarely happens when reflecting in diagonal mirror lines, so the answer must be B.

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.

Remember to reflect each vertex individually in the mirror line before you join up the points.

That's all for this lesson, thanks for watching.