september 14, 2009

Week 2

Day 5

An informal Introduction to Geometry

How many lines of symmetry to these regular polygons have?

Do you see a pattern?

opener

symmetric When you can fold a figure in half so that the two halves fit exactly on top of each other, the shape is symmetric.

line of symmetry The line that contains the fold

The horizontal line through the second T is not a line of symmetry

vertical line of symmetry

Symmetry

To be a line of symmetry, the shape must have two halves that match exactly.

When you trace a heart onto a piece of folded paper, and then cut it out, the two half hearts make a whole heart. The two halves are symmetrical.

Which of these flags have a line of symmetry?

United States of America Canada

Maryland England

What about these math symbols?Do they have symmetry?

# 1. Which other letters are symmetric? Which letters are both horizontally symmetric and vertically symmetric?

solution next slide

# 2. Describe the lines of symmetry of a circle.

any line through the center of the circle

You can look to see if your name has symmetrical letters in it too!

A B C D E FG H I J K L M N O P Q R S T U V W X Y Z

Infinite number

p. 10 # 6

p. 14 # 5

These two problems will be online on Mr. Patel’s school page.

p.10 # 6

p.14 # 5