Similar Figures and Proportions (4-8)

Similar Figures and Proportions

Vocabulary

Similar- figures that have the same shape, but not necessarily the same size. The symbol ~ means is
              similar to.

Corresponding Sides- corresponding sides of two or more similar polygons are in the same relative
                                    position.

Corresponding Angles- two or more similar polygons are in the same relative position.

Examples

Definition: Similar figures are figures that are the exact same shape, but are different sizes.

Similar figures	Not similar figures

Two figures are similar if the lengths of their corresponding sides form a proportion.

These two triangles are similar. We can prove that they are similar using a ratio table to compare the lengths of their corresponding sides.

Big triangle	Small triangle
20	15
8	6
16	12

• In the table, you can see that the ratio of the bases is 15/20. This reduces to 43.
• Also in the table you can see that the ratio of the two right sides is 6/8. This reduces to 43.
• Finally, the ratio of the two left sides is 12/16. This reduces to 43.

Since all three ratios are equivalent, then the two triangles are similar.
2015=86=1612
Therefore, the two triangles are similar.

 http://www.mathvillage.info/node/94

Video Help

https://www.youtube.com/watch?v=1O-ieOZ5y6s

https://www.youtube.com/watch?v=Sw9ctIFE2FM

http://www.showme.com/sh/?h=knG9X0a