Transformations · Year 11
In Year 11 you learn: negative and fractional scale factors.
A transformation moves a shape. Reflections, rotations and translations keep the size and shape the same (the image is congruent); an enlargement changes the size by a scale factor but keeps the shape (the image is similar).
Key facts
- Reflection: in a mirror line; in the x-axis (x, y) → (x, −y); in the y-axis (x, y) → (−x, y).
- Rotation: give the angle, direction and centre. 180° about the origin: (x, y) → (−x, −y).
- Translation: a column vector (a, b) means a right and b up.
- Enlargement: give the scale factor and centre; every length is multiplied by the scale factor.
- Areas scale by the scale factor squared.
Worked examples
Example 1
Describe the single transformation that maps triangle A onto triangle B.
Answer: A reflection in the y-axis (the line x = 0)