2. Similar Triangles
For two triangles to be similar one of the
following conditions apply:
Corresponding angles in the triangle are equal
Corresponding sides are in the same ratio
K McMullen 2012
3. Similar Triangles
Condition 1: Corresponding angles in the triangle
are equal
Remember that all internal angles within a
triangle add to 180 degrees
Triangles may need to be rotated so that you can
visualise the corresponding angles easily
K McMullen 2012
4. Similar Triangles
Condition 2: Corresponding sides are in the
same ratio
A'B’/AB
=B'C’/BC
=A'C’/AC
=k
k is the scale factor
K McMullen 2012
5. Similar Triangles
To test whether two triangles are similar:
Separate the diagram so you have two separate
triangles
Label your triangles (ABC for angles and abc for
corresponding sides)
Calculate the internal angles of both triangles
Or
Calculate the ratio of two corresponding sides
If the angles are the same or the corresponding
sides are the in the same ratio then the triangles
are similar
K McMullen 2012
