Lines of symmetry of an equilateral triangle

Step by step

The question

Question: how many lines of symmetry does an equilateral triangle have?

1 Try the folds

Imagine folding the shape along a line.

If the two halves match exactly, it is a line of symmetry.

Fold through a corner and the middle of the opposite side.

The halves match: line 1.

Fold through a corner and the middle of the opposite side.

The halves match: line 2.

Fold through a corner and the middle of the opposite side.

The halves match: line 3.

2 Count the lines

We found 3.

So an equilateral triangle has 3 lines of symmetry.

Careful!

Each fold goes through a corner and the middle of a side.

Count each fold once: 3, not 6.

3 Check

Let's check: a regular shape has as many lines of symmetry as sides.

3 sides, 3 lines.

Right!

Let's look back.

First: try the folds.

Then: count the lines.

Last: check.