Congruency, Enlargement and Combined Transformations · Form 5
What 'describe the transformation fully' requires
A full description names the single type of transformation and gives every detail that pins it down exactly, so that anyone could reproduce the image from your words alone.
Name the type, then give its data
Every full description has two parts: the name of the transformation and the specific information that makes it unique. Saying only 'a rotation' is not enough, because infinitely many rotations exist.
The marks come from the exact details that single out yours from all the others.
What each transformation needs
Translation: state that it is a translation and give the translation vector as a column vector (for example, 5 to the right and 2 down). Reflection: state reflection and give the equation of the axis of reflection, such as y = x.
Rotation: state rotation and give the centre, the angle, and the direction (clockwise or anticlockwise). Enlargement: state enlargement and give the centre and the scale factor.
Common mistakes
A description loses marks when a required piece is missing, an angle without a centre, or a rotation with no direction stated. Another error is naming more than one transformation for a single mapping, or using loose words like 'turn' or 'slide' instead of the proper terms.
For a combined transformation, describe each stage separately and in the correct order.
Source:DSKP KSSM Mathematics Form 4 and 5 (Versi English)
Frequently asked questions
What must I include to "describe the transformation fully" in the exam?
Name the exact type - translation, reflection, rotation, or enlargement - and give every defining detail: a translation needs the vector, a reflection needs the axis or line, a rotation needs the centre, angle, and direction, and an enlargement needs the centre and scale factor.
Why do I still lose marks even when I identify the transformation type correctly?
Marks are awarded for each specific detail, not just the type - so naming "rotation" without stating the centre, angle, and direction, clockwise or anticlockwise, loses marks. Missing even one required detail counts as an incomplete description in the marking scheme.
What's a common pitfall when a transformation involves two shapes far apart?
Students often confuse a translation with a combined transformation, or forget to check whether the shape has also been reflected or rotated, not just moved. Always compare orientation and size between object and image before deciding on a single transformation type.