Lesson video

Hi, I'm Miss Davies.

In today's lesson, we're going to be reflecting images in a diagonal line on the coordinate grid.

These lines will mostly be y equals x and y equals negative x.

Now that we're reflecting in a diagonal line on a coordinate grid.

We need to be very familiar with these two lines.

This is the line y equals x.

You can see that every point along this line, the x and the y-coordinates are the same.

This is the line y equals negative x.

You can see that the numerical value is equal, one coordinate is negative and one coordinate is positive.

For example, you could have negative two two, three negative three, negative one one or negative 72 72 would also be on this line.

In this example, we've been asked to reflect this rectangle in the line y equals x.

Let's start by drawing that line onto our grid.

We're going to work with one coordinate at a time.

Starting with this one.

This vertex is one diagonal square from the mirror line.

When reflected, it will be here.

Next, let's look at this one.

This is one and a half diagonal squares from the mirror line.

When reflected, it will be here.

We can then do this with our other vertices.

Then finally, join these together to show our reflected image.

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 in turn in the mirror line.

This will reduce the chance of you making a mistake.

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 you're reflecting each vertex in the mirror line individually, and then joining up the points.

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.

Quadrants are the four sections of a coordinate grid.

Quadrant one is in the top right.

Quadrant two is in the top left.

Quadrant three is the bottom left.

And quadrant four is the bottom right.

If we've got a polygon in quadrant two, that we'll reflect in the line y equals x, it is going to be in the diagonally opposite quadrant.

This is quadrant four.

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.

The line y equals x plus one, has a gradient of one and a y-intercept of one.

It looks very similar to y equals x.

It's just been moved up one unit.

That's all for this lesson.

Thanks for watching.