# Reflecting about Y = X and Y = -X (Ver 2)

- Author:
- Tim Brzezinski

- Topic:
- Coordinates, Geometry, Straight Lines, Reflection

## Here, the Mona Lisa is reflected about the LINE Y = X. Drag points B, C, and the pre-image picture around and observe how her reflection changes.

## In the app above, move Lisa around to get different primage points. Then, record their images in the image column.

Take a look at the table of data above. Suppose a point **( a, b) is reflected about the line y = x**. What would the coordinates of its image be? Express in terms of

**and**

*a*

*b*.## Here, the Mona Lisa is reflected about the LINE Y = -X. Drag points B, C, and the pre-image picture around and observe how her reflection changes.

## In the app above, move Lisa around to get different primage points. Then, record their images in the image column.

Take a look at the table of data above. Suppose a point **( a, b) is reflected about the line y = -x. **What would the coordinates of its image be? Express in terms of

**and**

*a*

*b*.