Lesson 24 — Activity 2: Reflections

Getting Ready

When you look in a mirror, you see a reflection. In a reflection, an object is flipped or reversed in comparison to the original object. For example, if the man lifts his left arm, the image appears to lift his right arm.

In this activity, you will look closely at reflections (flips).

You can see the reflected arm in this image.
Image courtesy of www.imagesgoogle.com

Graphs can also be reflected. They are usually reflected around the x-axis or the y-axis. In this activity, you will reflect all of your graphs around the y-axis.

Let's start by looking at a line segment. You are given the line segment below that goes from A (3,4) to B (5,8). You want to reflect it in the y-axis. Remember the y-axis is the vertical line that passes through 0 on the x-axis.

You will see how this line segment can be reflected.

The easiest way to do a reflection is to count how far each point is away from the y-axis, then count an equal number of squares on the other side of the y-axis, and draw a point there. You have to do this for each individual point.

You can see how the line segment has been reflected.

Notice that A and A' are an equal distance from the y-axis. Also note that B and B' are also an equal distance from the y-axis.

You can also do reflections with shapes. Let's look at reflecting a rectangle in the y-axis.

You will see how this rectangle can be reflected.

To reflect the rectangle, you must move each point an equal distance on the other side of the y-axis and redraw your picture.

You can see how the rectangle has been reflected.

Digging Deeper

Click here to see two more examples of reflections of shapes. The first page shows the original images and the second page shows where the reflections of the shapes are placed.