Mathematics 05807.1 Transformations
Transformations
Translate, reflect, rotate and enlarge a shape, with the full description an examiner wants shown alongside.
- Translation vectors
- Mirror lines
- Centre and angle of rotation
- Scale factor
Full description — what the exam wants
Translation by the vector (3, 2).
Predict
Which of these transformations changes the size of the shape?
Experiment
- 1Translate the shape by (3, 2), then read the full description. Note that a vector, not a distance, is required.
- 2Reflect in the y-axis and then in y = x, and see that the order matters.
- 3Rotate by 90° and then by −90°, and check the description names the angle, the direction and the centre.
- 4Set the enlargement scale factor to −2 and describe what a negative scale factor does.
Explain
Marks in these questions are for the full description, and each type has its own required parts:
- Translation — name it and give the column vector.
- Reflection — name it and give the equation of the mirror line.
- Rotation — name it and give the angle, the direction and the centre.
- Enlargement — name it and give the scale factor and the centre.
Missing any one of those parts loses a mark, and it is the commonest way to drop marks in the topic. “Rotation of 90°” is not a full description; “rotation of 90° anticlockwise about (0, 0)” is.
A negative scale factor puts the image on the opposite side of the centre and turns it through 180°, which is why it looks upside down.