Vocabulary

Transformation: A transformation is an operation that maps an original geometric figure, the preimage, onto a new figure called the image.

Reflection: A transformation where a figure is flipped over a line called a line of reflection.

Congruent: Figures that have the same shape and same size. 

Concept

Recognize if a figure is reflected over the x or y-axis. 

Rules

When part of the graph is flipped over the horizontal axis, it is reflected over the x-axis. 

When part of the graph is flipped over the vertical axis, it is reflected over the y-axis. 

Example

The image below is reflected over which axis. 

Solution

As shown in the picture, the top part of the graph is flipped over the horizontal axis, which is the x-axis. We can also see from the coordinates (a,b) and (a,-b) that only the y value changed, which is a trait of x-axis reflection. 

Pre-requisite Skills

Reflection (5.13.9)