A line of symmetry is a straight line that divides a shape into two identical mirror image halves. Drawing lines of symmetry correctly requires careful observation of the shape and accurate placement of the line.

 

 

What a Line of Symmetry Shows

A line of symmetry shows that:
• each point on one side of the line matches a point on the other side
• corresponding points are the same distance from the line
• the two halves would fit exactly if folded along the line

 

Only straight lines can be lines of symmetry.

 

 

How to Draw a Line of Symmetry

To draw a line of symmetry on a shape:

• look for a line that splits the shape into two equal halves
• check that both sides are mirror images
• draw the line straight through the centre of the shape
• extend the line fully across the shape

 

The line must divide the shape evenly.

 

 

Checking a Line of Symmetry

To check whether a line is a line of symmetry:

• imagine folding the shape along the line
• check whether the edges and features match exactly
• confirm that no part is left unmatched

 

If any part does not match, the line is not a line of symmetry.

 

 

Examples in Common Shapes

A square has four lines of symmetry:
• one vertical
• one horizontal
• two diagonal

 

A rectangle has two lines of symmetry:
• one vertical
• one horizontal

 

An isosceles triangle has one line of symmetry.

 

A scalene triangle has no lines of symmetry.

 

A circle has infinitely many lines of symmetry, all passing through the centre.

 

Irregular shapes may have no lines of symmetry.

 

 

Drawing Multiple Lines of Symmetry

Some shapes have more than one line of symmetry.

 

Each line must be drawn separately and must still divide the shape into two identical halves.

 

Do not assume symmetry without checking carefully.

 

The appearance of symmetry must be confirmed by matching both sides

 

 

Key Points to Remember

A line of symmetry splits a shape into two identical mirror halves.
Only straight lines count as lines of symmetry.
Some shapes have more than one line of symmetry.
Not all shapes have lines of symmetry.
Always check symmetry by imagining a fold along the line.

 

Being able to draw lines of symmetry accurately helps describe and analyse shapes clearly in geometry.