Download Example

1. Quiz  THURSDAY
2. Pick Up C1
(even if you did not get it signed)
3. Notes – Lesson 37
4. PRACTICE, PRACTICE, PRACTICE
Perimeters, Angles, Areas…
We classify polygons according to
their number of sides
Number of Sides
Name
3
Triangle
4
Quadrilateral
5
Pentagon
6
Hexagon
7
Heptagon
8
Octagon
9
Nonagon
10
Decagon
11
Hendecagon
12
Dodecagon
The number of sides is equal to the number of angles
The sum of the interior angles in a polygon is:
S = (n-2) x 180˚
(n is the number of sides!)
Example
What is the sum of the interior angles of a hexagon?
n=6
S = (6-2) x 180˚
S = 4x180˚
S = 720˚
The measure of ONE angle in a polygon is:
S÷n
(this only works if all the sides are equal)
Example
What is measure of one angle in a perfect nonagon?
n=9
S=(9-2)x180
S = 1260
Each side: 1260 / 9 = 140
A diagonal is a segment that joins two vertices that
are not beside each other:
Plus MANY
more!
A bisector divides something into two equal parts:
EXAMPLE
Find the missing angle
˚
Step 1: Find n
n=5
Step 2: Find sum
S = (5-2) x 180˚
S = 3 x 180˚
S = 540˚
Step 3: Find missing angle
540-80-115-105-100
=140˚
EXAMPLE
Step 1: Find n
Find the missing angle
n=6
Step 2: Find sum
S = (6-2) x 180˚
S = 4 x 180˚
S = 720˚
Step 3: Find the missing
interior angle
720-140-110-130-115-110
=115˚
Step 4: Find the missing
exterior angle
=180-115
=65˚
EXAMPLE
How many sides does a polygon have if the
sum of the interior angles is 2340˚?
(S ÷ 180) + 2 = n
(2340 ÷ 180) + 2 = n
13 + 2 = n
15 = n
1. Learning Activity #37 (use workbook p.128)
2. Polygon Worksheet
3. Workbook p.129 #3
p.132 #1
p.133 #4
p.134 #7
p.135 #9