Transcript similar polygons

Warm-Up
• If ∆QRS  ∆ZYX, identify all 3 pairs of
congruent angles and all 3 pairs of
congruent sides.
Geometry 7-2
Similar Polygons
Definition
Figures that are similar (~) have the same
shape but not necessarily the same size.
Definition
• Two polygons are similar polygons if and
only if:
– Corresponding angles are congruent
– Corresponding side lengths are proportional
Example
Show that the following triangles are similar.
Definition
A similarity ratio is the ratio of the lengths of
the corresponding sides of two similar polygons.
The similarity ratio of ∆ABC to ∆DEF is
, or
The similarity ratio of ∆DEF to ∆ABC is
, or 2.
.
Definition
• A similarity statement is a statement that
declares two figures similar.
• ∆ABC ~ ∆DEF