Triangles
Take a
rectangular
piece of paper.
Take a
rectangular
piece of paper.
Fold it in half
Take a
rectangular
piece of paper.
Fold it in half
Use a ruler to
draw a line
from the top of
the fold to the
bottom right
hand corner.
Take a
rectangular
piece of paper.
Fold it in half
Use a ruler to
draw a line
from the top of
the fold to the
bottom right
hand corner.
Cut along the
line.
You should now have 3 triangles
Can you prove that this is a line
of symmetry?
Does this triangle have any other
line of symmetry?
No it doesn’t. It only has the one.
How can we prove that line ac is equal to line bc?
By folding along the line of symmetry. If you haven’t tried it, do it now.
d
b
a
c
d
a
b
b
This type of triangle,
where two sides are
equal, has a special
name.
It is called an
ISOSCELES triangle
c
d
a
b
b
Stick this triangle
into your jotter and
name it ISOSCELES
triangle.
Now use the other
two pieces of the
rectangle to make
another isosceles
triangle.
c
Your new triangle should look like this.
How do we know it is isoscles?
Which of these triangles do you think is isosceles?
These are the isosceles triangles.
Write in your jotter how we can
describe an isosceles triangle
and how we can prove it is
isosceles.