Congruency, Enlargement and Combined Transformations
Reflection
A transformation that flips a shape across a line to give a mirror image.
| English | Reflection |
|---|---|
| Bahasa Melayu | Pantulan |
| 中文 | 反射 |
How it is used
Reflect the point A(2, 5) in the x-axis. The image is A′(2, −5), because reflecting in the x-axis keeps x the same and changes the sign of y.
Where it shows up in SPM
An isometric transformation in this Form 5 chapter. Paper 2 asks you to draw an image reflected in a given line, or to describe a reflection by naming its axis (for example y = x or x = 3).
It also appears as a step inside combined transformations.
Don't confuse it with
Open the chapter: Congruency, Enlargement and Combined Transformations →
Frequently asked questions
How do I find the axis of reflection?
Join a point to its image and find the midpoint; the axis is the perpendicular bisector of that line. The axis is equal distance from the object and image, and every object–image pair shares the same axis.
What happens to a point on the axis itself?
A point lying on the mirror line does not move; it maps to itself. This is a useful check: if part of your shape sits on the axis, that part must stay in exactly the same place in the image.