Key learning points

1. A congruent shape has not changed size
2. Two shapes can be congruent even if one has been reflected or rotated
3. An image can be described in terms of its object
4. The description states how the object has been changed

Common misconception

Keywords

• Object - The object is the starting figure before a transformation has been applied.

• Image - The image is the resulting figure after a transformation has been applied.

• Transformation - A transformation is a process that may change the size, orientation or position of a shape.

• Congruent - If one shape can fit exactly on top of another using rotation, reflection or translation, then the shapes are congruent.

• Invariant - A property of a shape is invariant if that property has not changed after the shape is transformed.