Understand Lines of Symmetry

In this activity, we will look at lines of symmetry!

 

A line of symmetry is a line which cuts a shape exactly in half.

That means the two halves are exactly the same, and if we put them together, one would lie perfectly on top of the other. 

 

We draw them on a shape with a dashed line  - - - - - - - - - -

 

 

 You can see that the square above could be folded along each of the dotted lines shown and both sides would be identical!

We can say that a square has four lines of symmetry.

 

Let's look at another shape.

 

Example

How many lines of symmetry does a rectangle have?

 

 

Answer

To start with we have a horizontal line and a vertical line - easy!

 

 

What about the diagonals, like the ones in the square?

 

 

We can see that the two halves look the same, but they would not fit on top of each other if we folded them!

Try it by using a rectangular sheet of paper.

Fold it diagonally

Do the two triangles fit together?

 

 

You will see that the corners (vertices) do not fall exactly on top of each other!

Therefore, a rectangle has just two lines of symmetry!

 

Let's try some questions with different shapes!