1. Reflection
GM4.1 Core Plenary
Investigate what happens to the coordinates of point A when it is reflected in the x-axis to give B and then this image is reflected in the y-axis to give C.
In other words, what effect does the mapping A → C have on the coordinates of A?
Preamble
A short investigation into what happens to coordinates when points are reflected in x- and y-axes. Pupils should be reminded that they only have about five minutes or so to come up with a result, and that sketch grids are all that are needed to get accurate answers if they use what they have just learnt about reflections. Some pupils may need a little support with the concept of a reflection of a reflection. Negative coordinates arise quite naturally, but encourage pupils to select positions of A in all four quadrants.
Possible content
Reflection of points, coordinates.
Resources
Squared paper for helping pupils draw coordinate grids.
Solution/Notes
(x, y) → (−x, −y)
A possible short homework task might be to investigate what happens if the first reflection is in the y-axis followed by a reflection in the x-axis (order of reflection commutes in this case).