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

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27 Problems