# Rotations on a Coordinate Plane

By Marilyn Mears on Apr 24, 2017

Although visually impaired students use rotation terms in mobility lessons (e.g, make a quarter turn) they may not know how to graph rotations.  This lesson gives them practice rotating shapes on a coordinate grid.  It also provides some rules to use when you know the ordered pairs.

• Make sure students understand coordinate grids, how to read ordered pairs, and how to plot points.

## Materials

• toy pinwheel for demonstration of rotation

## Procedure

Show pinwheels as examples of rotations.  The shapes are congruent, but in different positions because of the rotation.  Every rotation has a center point.
1. Provide shapes cut out of heavy cardboard.   Put on a piece of corrugated cardboard or a graph board.  Put a pin in the shape either on a corner or in the center of the shape.  Show how the shape can rotate around the pin just like the pinwheel.   Try rotating the shape approximately 90 degrees, 180, 270, or 360 degrees as in mobility ( 90 degree turn) and observe where the shape is.   Make sure students try clockwise and counterclockwise rotations.  Students could also stand up and rotate themselves to demonstrate understanding of a 90 or 180 degree turn.
2. Plot the following points on a graph paper(print or braille graph paper), graphing calculator, or iPad graphing app.  (2,4), (4,4), and (4,1)  Connect the points to form a triangle.
3. Rotate the triangle clockwise 90 degrees over the origin.  Do this by rotating the whole graph one quarter turn.  Orient the student to the new x and y axes and write the coordinates of the points after the 90 degree rotation.  (see pictures)
4. Notice that the points for Triangle A'B'C' become A'(4,-2), B' (4,-4), and C' (1,-4)
5. Check using the formula for a 90 degree rotation:  (x,y) = (y,-x)
6. Try other examples as needed.    IMG_0168.JPG, IMG_0169.JPG
Attached File(s): IMG_0168.JPG IMG_0169.JPG