# Performing and Describing Transformations

At the start of this unit students learn how to perform and describe reflections, rotations, translations and enlargements on a grid.  As learning progresses they are challenged to describe a combination of transformations using the correct terminology.

This topic takes place in Year 9 Term 5 and is followed by transforming graphical functions.

##### Revision Lessons

Prerequisite Knowledge

• Use conventional terms and notations: points, lines, vertices, edges, planes, parallel lines, perpendicular lines, right angles, polygons, regular polygons and polygons with reflection and/or rotation symmetries;
• Identify an order of rotational and reflective symmetry for two dimensional shapes
• Use the standard conventions for labelling and referring to the sides and angles of triangles; draw diagrams from written description
• Recognise linear functions in the form y = ± a and x = ±

Success Criteria

• Identify, describe and construct congruent and similar shapes, including on coordinate axes, by considering rotation, reflection, translation and enlargement (including fractional and negative scale factors)

Key Concepts

• An object is transformed to create an image.
• Rotation, Translation and Reflections involve congruent objects and images whereas enlargement leads to the object being similar to the image.
• Translation vectors are used to describe movements along Cartesian axes.
• When reflecting objects the image is always the same distance from the line of reflection as the object.
• Rotations and enlargements are constructed from a centre.
• A negative scale factor transforms the object through the centre.

Common Misconceptions

• Translation vectors can incorrectly be written using the name notation as coordinate pairs.
• Translations, Rotations, Enlargement and Reflections all come under the umbrella term of transformation. Students often confuse the term translation for transformation.
• Students often have more difficulty describing single transformations rather than performing them.
• Enlargements can involve making a shape smaller as well as bigger. Fractional scale factors between 0 and 1, not negative, decrease the size.

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