Geometry · Transformations
Line of Symmetry
HSG-CO.A.3
Definition
A line that divides a figure into two halves that are mirror images.
Examples
- Folding a figure along its line of symmetry makes the two halves match exactly.
- A square has four lines of symmetry.
Key rule
A figure's two halves must match exactly when folded along the line of symmetry.
Memory hook
Fold along it — the halves match perfectly.