Congruency, Enlargement and Combined Transformations
Centre of enlargement
The fixed point from which an enlargement is measured.
| English | Centre of enlargement |
|---|---|
| Bahasa Melayu | Pusat pembesaran |
| 中文 | 放大中心 |
How it is used
Enlarge A(2, 1) about the centre of enlargement C(0, 0) with scale factor 3. Multiply each coordinate by 3 from C to get A′(6, 3); the distance CA′ is three times the distance CA.
Where it shows up in SPM
Central to enlargement questions in this Form 5 chapter. Paper 2 gives the centre and scale factor for you to draw the image, or gives object and image for you to find the centre by drawing rays through matching points.
Describing an enlargement fully always requires the centre.
Don't confuse it with
Open the chapter: Congruency, Enlargement and Combined Transformations →
Frequently asked questions
How do I find the centre of enlargement?
Draw a straight line through each object point and its matching image point, then extend the lines. The point where all the lines meet is the centre of enlargement, because every object point, its image and the centre lie on one straight ray.
Does the centre of enlargement move?
No. The centre is an invariant point, meaning it maps to itself and stays exactly where it is.
If a vertex of the object sits on the centre, that vertex does not move in the image.