We will consider two types of symmetry:

• Reflective symmetry; and
• Rotational symmetry.

Reflective Symmetry

A shape has reflective symmetry, if you can draw a line such that one side of the line is the mirror image of the other side.

We need to consider two types of questions. Firstly if we are given a line of symmetry and part of a shape, we must be able to draw the rest of the shape. Secondly we should be able to identify the lines of symmetry of a given shape.

Let’s try the first type of question together below:

And let’s try the second type of question here:

Exercise

Now let’s complete questions 2 to 4 of exercise 3H on page 51 of the textbook:

The answers are below:

Rotational Symmetry

With rotational symmetry we say that a shape has rotational symmetry with a specific order, where the order is the number of times the shape looks the same if we rotate it around its central point.

Let’s find the order of rotational symmetry of the following shapes:

Exercise

Let’s try exercise 3I on pages 52 and 53 of the textbook:

The answers are below: