1. Honors Geometry Jan 2012
WARM UP- THINK- 3 minutes silently PAIR- chat with a partner 1. If a vertical line of symmetry is drawn through this trapezoid, what is the shape of each resulting half? a) rhombus c) parallelogram b) rectangle d) trapezoid 2. Find x:

2. objective Homework Due Tuesday pg. 443: 1- 8, 15, 16
students will derive and apply the formula for the area of a regular polygon
students will take notes, participate in class discussion and use think-pair-share
Homework Due Tuesday
pg. 443: 1- 8, 15, 16

3. Project See handout
PROJECT DUE: FEBRUARY 6

4. Area formulas:
Regular Polygons ?

5. Areas of Regular Polygons
Read pg 442
Do investigation--complete handout
words to know: apothem
circumscribed circle

6. 3as 5 6 7 …. 12 n 6as apothem Number of sides a
Area of regular polygon
3as
6as

7. Regular Polygon Area Conjecture
Chapter 8 Area Formulas
Term
Definition
Example
apothem
A perpendicular segment from the center of the polygon to a side of the polygon
Regular Polygon Area Conjecture
The area of a regular polygon is given by the formula
Where A is the area, s is the side measure, n is the number of sides, a is the apothem
Where A is the area, P is the perimeter and a is the apothem

8. because P = sn
Do problems pg. 443: 11, 14

9. debrief
what is the formula for finding the area of a regular polygon and how did we derive it? what is the apothem? what letter do we use to represent it? why don’t we just call it “h”? what is “s” in the formula? why don’t we just call it “b”? what will you do to help yourself remember the formulas?