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Students will be able to identify and apply
similar polygons
You can use ratios and proportions to
decide whether two polygons are similar
and to find unknown side lengths of similar
figures.
Have the same shape but not necessarily
the same size
Is similar to is abbreviated by ~ symbol
Two Polygons are similar if corresponding
angles are congruent and the
corresponding sides are proportional
Like congruence statements, the order
matters so if two figures are similar, their
corresponding parts should be in the same
order
If ΔABC ~ ΔDEG then <A ≅ <D
and AB ~ DE
Use when three or more ratios are equal
AB = BC = CD = AD
GH HI IJ GJ
Scale Factor: ratio of corresponding linear
measurements to two similar figures
(ratio of corresponding sides in simplest
form)
What are the pairs of congruent angles if
ΔABC ~ ΔRST?
What is the extended proportion for the
ratios of corresponding sides for ΔABC ~
ΔRST?
ABCD ~ EFGD
What is the value of
x?
What is the value of
y?
Your class is making a poster for a rally.
The poster’s design is 6in. high by 10 in.
wide. The space allowed for the poster is
4 ft high by 8ft wide. What are the
dimensions for the largest poster that will
fit in the space?
What if the dimensions of the largest
space was 3 ft high by 4 ft wide?
All lengths are proportional to their
corresponding actual lengths
Scale: ratio that compares each length in
the scale drawing to the actual length
Where have you seen a scale?
The diagram shows a scale drawing of the
Golden Gate Bridge. The distance
between the two towers is the main span.
What is the actual length of the main span
of the bridge if it is 6.4 cm in the drawing?
Pg. 375
# 1 – 18, 21 – 28, 32
27 Problems
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