Download G_PP_8-2_SimilarPolygons

Similar Polygons
Geometry 8-2
• Similar Figures – Same shape but not
necessarily the same size
Vocabulary
• Get your supplies
- Patty Paper
- Ruler
- Handout
Similarity Exploration
• Use Patty paper to
compare all the angles
• How do the
corresponding angles
compare?
• They are congruent
Similarity Exploration
• Measure the corresponding
segments in each polygon –
Use metric
• Find the ratios of the
corresponding sides
• (Small Side)/(Large Side)
Similarity Exploration
• What did you learn about the
ratios of the sides?
Similarity Exploration
• Two polygons are similar if and only if the
corresponding angles are congruent and
the corresponding sides are proportional
• Similar polygons are shown as follows
Similar Polygons
• Two polygons are similar if and only if the
corresponding angles are congruent and
the corresponding sides are proportional
Note: For similar polygons you
must have BOTH congruent
angles and proportional sides
Similar Polygons
Example
Example
Example
Example
Example
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Practice
Similar Polygons
• Get your supplies
- Patty Paper
- Ruler
- Graph Paper
Similarity Exploration
• Copy this figure
onto your own
graph paper
• Pick one of the
following scale
factors
½ , ¾ , 2, 3
Similarity Exploration
• Multiply the
coordinate of
each of the
vertices by your
scale factor
Similarity Exploration
• Plot each of
these new
points
• The scale factor
is the dilation of
your figure
Similarity Exploration
• Compare the
lengths of the
sides
• How do these
ratios compare
to the scale
factor?
Similarity Exploration
• If one polygon is a dilated image of
another polygon, then the two polygons
are similar
Dilation Similarity
SAMPLE PROBLEMS
• Pages 425 – 428
• 7, 8, 9, 11, 15, 18, 21, 23, 27, 33
Homework
• Pages 425 – 428
• 7, 8, 9, 11, 15, 18, 21, 23, 27, 33, 52
Honors Homework