Edexcel IGCSE Maths 复习笔记 5.2.1 Transformations - Rotation

What are transformations in maths?

• There are 4 transformations in GCSE Maths – rotation, reflection, translation and enlargement
• All 4 change a shape in some way, useful in things like computer graphics.
• There is some language and notation often used in this topic – the original shape is called the object and the transformed shape is called the image
• Vertices on the object are labelled A, B, C, etc.And on the image they will be A’, B’, C’ etc.If there is a second transformation then they will become A”, B”, C” etc.

Rotation – what do I need to know?

• You need to be able to perform a rotation (on a coordinate grid) as well as spotting and describing a rotation when presented with one
• Rotation has 3 features:

1. Angle of rotation – how far we are going to rotate the shape by

2. Direction – clockwise or anti-clockwise

In the special case of 180° you will not need a direction

3. Centre of rotation – this is the point about which our rotation happens

It does NOT have to be a point that is on the shape nor in the middle of the shape; it can be anywhere