A line of symmetry splits a shape into two halves that are mirror images. If you fold the shape along the line, the two halves match exactly.
Some shapes have more than one line of symmetry. A square has 4, a rectangle has 2 and an equilateral triangle has 3. A regular shape with n sides has n lines of symmetry. Some shapes, like a scalene triangle, have none.
Worked example
How many lines of symmetry does a regular hexagon have?
- A regular shape with n sides has n lines of symmetry.
- A hexagon has 6 sides.
Answer:6
Key words
- symmetry
- both halves match like a mirror
- line of symmetry
- the fold line
- regular shape
- all sides and angles equal
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Common Core-referenced: 4.G.A.3