## Tuesday, February 26, 2013

### Day 102: The Venn Diagram

Continuing where we left off with the discovery of the parallelogram yesterday, I began class by building a Venn diagram of "4 sided shapes" (didn't want to burden them with the Q-word just yet). So if all squares must fit inside the rectangle category, and all rectangles must fit inside the parallelogram category, if we look at the major properties (squares have equal sides AND 90 deg angles, while rectangles only have the 90 deg angles), that must mean there's another class of parallelograms that has equal sides. I tried to create a genetic/inherited trait metaphor and use the idea that squares are the child of rectangles and this new shape. Most students knew the name rhombus, but the power of the metaphor was helpful in "guessing" the properties that would hold true for it without the investigation.

For example, if the diagonals of squares are angle bisectors, but is NOT true for rectangles, then where did squares get that trait from? Must have been the rhombus!

What was incredibly frustrating was that as I was creating the diagram with circles (as one generally does with a Venn diagram), I had a lot of students puzzled as to why I was pointing to a circle and labeling it "rectangles." Seriously. I couldn't make this up. My hope was that once I finished, they would see the Venn diagram and recognize it from the rest of the world and all would be right again. Nope. It wasn't until I used the name 'Venn' that any connections were made. *sigh*

Unit 7 Worksheet 1 was also assigned in preparation for the expected snow day tomorrow.