Take
a look at the letter below--half of it is missing. See if you can guess
what letter it is and then click the button below it to see if you were
correct.
After
you clicked the button the right half of the letter A appeared.
It looked exactly the same as the left half! Because
the two sides of the A look the same, or mirror each other, we
say that the A has line symmetry.
We call it line symmetry because we can actually draw a line down
the middle of the A that divides the letter into two mirror images.
That line is called
the line of symmetry. We could also fold
the A on the line of symmetry and the two halves would fit perfectly
on top of each other!
Many letters have
more than one line of symmetry. The letter below has two lines of symmetry.
See if you can guess what letter it is and then click on the button. It
will show you two lines of symmetry.
The letter H also
has line symmetry, but it has another kind of symmetry
as well. Notice the yellow star on the H below. Make a note of
where it begins and watch where it ends up after you click on the button.
The yellow star ended
up on the bottom right of the H after it rotated. Even though
it was in a different place, the H still looked the same. When
a figure looks the same after it is rotated, we say that it has
rotational symmetry. The key though is
that the letter (figure) cannot rotate a full turn. It must be
less than a full turn.
Does
the letter W have rotational symmetry?
The letter
W does not have rotational symmetry because it does not look the
same after it is rotated.
Check Your Understanding
Does the letter N have rotational
symmetry?
Make an educated guess and then push the button to find out.
