Similar Polygons + Triangles Review

Similar Polygons + Triangles Review

Recap

In one of our previous lessons, we determined if two polygons were similar or not based on their side lengths

Multiple Choice

What had to be true about their side lengths for the figures to be similar?

• They had to be the same size

• The corresponding sides had to be proportional

Open Ended

What were we looking for when we were trying to determine whether or not the figures were proportional?

Hint: There are two names for it

S ____ F_____

or

S_________ R____

Similar Figures

In order for polygons, or figures, to be similar, their side lengths must be proportional, or they must have the same scale factor.

Multiple Choice

Similar or not similar?

• Similar

• Not Similar

Multiple Choice

Similar or not similar?

• Similar

• Not Similar

Fill in the Blank

The following figures are similar, what is their scale factor, or similarity ratio?

Fill in the Blank

The following figures are similar, what is their scale factor, or similarity ratio?

Similar Triangles

After we practiced with similar polygons, we used our knowledge of proportions to use the Triangle Proportionality Theorem.

Example

•  $\frac{6}{x}=\frac{8}{5}$  

•  $8x\ =\ 30$  

•  $x\ =\ 3.75$  

Similar Triangles

Then, we used our knowledge of scale factors to utilize the Converse of the Triangle Proportionality Theorem.

Example 2

• Say we have this triangle. What is our proportion set up?

•  $\frac{AD}{DC}=\frac{BE}{EC}\ or\ \frac{DC}{AD}=\frac{EC}{BE}$  

•  $\frac{16}{20}=\frac{12}{15}$  or  $\frac{20}{16}=\frac{15}{12}$  

•  $\frac{4}{5}=\frac{4}{5}\ or\ \frac{5}{4}=\frac{5}{4}$  

• Since the scale factors are the same,  $AB\ \parallel\ DE$  

Multiple Choice

Find the value of x

• 7

• 7.5

• 8

Multiple Choice

Find the value of x

• 6

• 16

• 26

Multiple Choice

Determine whether

 $PS\ \parallel\ QR$  

• Parallel

• Not Parallel

Multiple Choice

Determine whether

 $MN\ \parallel\ GH$  

• Parallel

• Not Parallel

Practice: 10 - 15 Minutes

Use the Classkick from Thursday (12/17) and Friday (12/18) to practice with Similar Polygons + Similar Triangles

Poll

I feel ready to move onto the lesson on Thursday.

• S.O.S

• I'll be in small groups tomorrow

• I'M READY

• I feel okay