We can use coordinates to describe points and find patterns in the coordinates of transformed points.
We can describe a translation by expressing it as a sequence of horizontal and vertical translations.
For example, segment AB is translated right 3 and down 2.
Reflecting a point across an axis changes the sign of one coordinate.
For example, reflecting the point A whose coordinates are (2,-1) across the x-axis changes the sign of the y-coordinate, making its image the point A’ whose coordinates are (2,1). Reflecting the point A across the y-axis changes the sign of the x-coordinate, making the image the point A’’ whose coordinates are (-2,-1).
Reflections across other lines are more complex to describe.
We don’t have the tools yet to describe rotations in terms of coordinates in general. Here is an example of a 90∘ rotation with center (0,0) in a counterclockwise direction.
Point A has coordinates (0,0). Segment AB is rotated 90∘ counterclockwise around A. Point B with coordinates (2,3) rotates to point B’ whose coordinates are (-3,2).