Geometry Session 8: Similarity

Session 8, Part A:
Scale Drawings (50 minutes)

In This Part: Finding a "Good Copy" | Doubling the Coordinates | Distances and Angles

Here is a picture of a panther:


Problem A1
Which of these pictures is a good copy of the original picture? Explain how you made your decision.

Try to come up with a method of comparing the pictures that will tell you whether a picture is distorted. For example, you may want to look at the ratio of length to height. Looking at angles would be another method. Close Tip

Video Segment
In this video segment, participants explore different ideas that will help them decide which copy is the best copy of the original picture. Watch this segment after you've completed Problem A1.

Compare your method with those the participants used in the video.

If you are using a VCR, you can find this segment on the session video approximately 3 minutes and 3 seconds after the Annenberg Media logo.

Mathematicians use the word "similar" to describe two figures that are the same shape but not necessarily the same size. If one is a scaled copy of the other, then the two figures are similar.

Two polygons are similar if and only if corresponding angles have the same measure and corresponding sides are in proportion.

Problem A2

Are these two rectangles similar? How do you know?

Problem A3

Are these two triangles similar? How did you decide?

Next > Part A (Continued): Doubling the Coordinates

Session 8: Index | Notes | Solutions | Video