Understanding Symmetry and Lines of Symmetry
What is Symmetry?
Imagine folding a piece of paper in half. If both sides match up perfectly, like mirror images, then the shape has symmetry! The fold line is called the line of symmetry or axis of symmetry.
The Mirror Test
Think of the line of symmetry as an invisible mirror. One half of the shape is the exact reflection of the other half. Every point on one side has a matching point on the other side, the same distance from the line.
Key Ideas:
- Both halves must be exactly the same
- They must be the same distance from the line
- They face opposite directions (like in a mirror)
- Some shapes have more than one line of symmetry
- Some shapes have no lines of symmetry
Types of Symmetrical Figures
One Line of Symmetry
This triangle has exactly one line of symmetry going down the middle.
Multiple Lines of Symmetry
A square has four lines of symmetry!
No Lines of Symmetry
This shape has no lines of symmetry - no way to fold it to match perfectly.