Which diagram shows the correct reflection of the image?

Reflecting in a Given Horizontal or Vertical Line

﻿Hi, I'm Ms. Davies. In this lesson today, we're going to be looking at reflecting objects in horizontal and vertical lines on coordinate grids. This question is asking us to reflect the triangle in the x-axis. The x-axis runs left to right. We're going to look at each vertex intern. Let's start with the top one. This vertex is one square from the mirror line. When reflected, it will be one square on the other side of the mirror line. This next vertex is four squares from the mirror line. When reflected, this point will be four squares on the other side of the mirror line. From this information, I know that this is going to be our other vertex. We can check this to make sure. The left hand vertex is four squares from the mirror line. The reflected point is also four squares from the mirror line in the same x-coordinate as the initial Vertex. So it is correct. Let's join these vertices together to form our reflected triangle. In this next part, we've been asked to reflect the original triangle in the line x equals -1. At every point on this line, the x-coordinate is -1. This is the line x equals -1. To reflect the original triangle, we're going work again with each vertex intern. Let's start with the top one. The top vertex is three squares from the mirror line. When it is reflected, it will be three squares on the other side of the mirror line. Next, let's look at the left hand vertex. This is two squares from the mirror line, so it will be reflected two squares on the other sides. From this information, we can then draw our third point of the triangle. We can now join up the three vertices to give our reflected triangle. With this next question, we're reflecting the triangle in the y-axis. The y-axis runs up and down. The right hand vertex of our triangle is two squares from our mirror line. When we reflect the triangle, this point will be two squares on the other side of the mirror line. Our top vertex is four squares from the mirror line. We can then say that this will be four squares on the other side of the mirror line. The fifth and final vertex is also four squares from the mirror line. We can use this information to draw our reflected triangle. Next, we're reflecting the triangle in the line y equals 1. On this line, all of the points have a y-coordinate of 1. The base of the triangle is one square from the mirror line, so this will be one square on the other side of the mirror line when reflected. The top vertex of the triangle is four squares from the mirror line. When reflected, it will be four squares on the other side of the mirror line. Using this information, I have drawn our reflected triangle. 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, the x-axis goes across and the y-axis goes up and down. Make sure that your images are the same distance from the mirror linen in each question. 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 the images are the same distance from the mirror line, but they are fully reflected. In this example, we've been asked to identify the mirror line. This could also be asked as describing the transformation. We're looking for the points that the same distance from corresponding vertices in each triangle. The right vertex on the left triangle is corresponding with the left vertex in the right hand triangle. The point that is halfway between these vertices is here. If we next look at the top vertices in the triangles, these are corresponding with each other. This is the point that is the same distance from each vertex. If we join these points together, this is the line that we've got. We just need to check that this line is the mirror line for the third and final vertex in each triangle. We can see that the distance between this final vertex and the mirror line is four squares for each triangle. This means, this is our mirror line. This line is x equals 1. In this example, we've been asked to identify the mirror line. We're looking for the point that the same distance from the corresponding vertices of each of the rectangles. If we look at the left hand vertices, this is the point that is the same distance from each one. It is one square from the inside vertices, and it is two squares from the outside vertices. Then, looking at the right hand with vertices, this is the point that is in the middle of the corresponding vertices. If we join these points together, it gives us this line. This is the line y equals 2, this is our 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 your mirror line is the same distance from each of the reflected images. 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. When you reflect this shape in the x-axis, the x-coordinate will stay the same, but the y-coordinate is being multiplied by -1. When it's reflected in the y-axis, the y-coordinate has stayed the same and the x-coordinate has been multiplied by -1. That's all for this lesson. Thanks for watching.

1. A rectangle, labelled A, is being reflected in the line y = 1. Which diagram shows the correct reflection?

2. A triangle, labelled B, is being reflected in the line x = -2. Which diagram shows the correct reflection?

Identify the mirror line of the reflection shown.

In this lesson, we will reflect shapes across horizontal or vertical lines on a coordinate grid. We will extend our knowledge of reflections by using mathematical vocabulary to describe reflections in the coordinate plane.

Lesson overview:Reflecting in a given horizontal or vertical line (Part 2)

Core Content

Reflection: