**Similar Triangles**

If two shapes are similar, one is an enlargement of the other. This means that
the two shapes will have the same angles and their sides will be in the same
proportion (e.g. the sides of one triangle will all be 3 times the sides of the
other etc.).

angle A = angle D

angle B = angle E

angle C = angle F

AB/DE = BC/EF = AC/DF = perimeter of ABC/ perimeter of DEF

Two triangles are similar if:

1) 3 angles of 1 triangle are the same as 3 angles of the other

or 2) 3 pairs of corresponding sides are in the same ratio

or 3) An angle of 1 triangle is the same as the angle of the other triangle and
the sides containing these angles are in the same ratio.

*Example*:

In the above diagram, the triangles are similar. EF = 6cm and BC = 2cm . What is
the length of DE if AB is 3cm?

EF = 3BC, so DE = 3AB = 9cm.

© Matthew Pinkney