Download 2.3-2.4 Polygons!.

2.3/2.4 Polygons!
Learning Objective: to identify properties of polygons, and to
find the sums of the measures of the interior and exterior
angles of polygons
Warm-up (IN)
Do you know the term for…
1. A 3-sided figure?
2.A 4-sided figure?
3.A 5-sided figure?
4.A 6-sided figure?
5.A 7-sided figure?
6.…????
Notes
Polygon - A closed plane figure whose sides are segments
that intersect only at their endpoints.
Put the terms that you don’t know (by heart!!) in
your notes. Key terms on the left!
# of sides
3
4
5
name
triangle
quadrilateral
pentagon
6
hexagon
7
heptagon
8
octagon
9
nonagon
10
decagon
n
n-gon
Learning Objective: to identify properties of polygons, and to find the sums of the
measures of the interior and exterior angles of polygons
Concave Polygon -
Convex Polygon -
“caves” in
doesn’t “cave” in
Equilateral Polygon - All sides equal
Equiangular Polygon - All angles equal
Concave decagon
Convex hexagon
Regular Polygon - All sides and angles equal
regular hexagon
Learning Objective: to identify properties of polygons, and to find the sums of the
measures of the interior and exterior angles of polygons
To name a polygon - Name vertices in consecutive order!
O
U
H
E
S
Pent. HOUSE
or Pent. OUSEH
CKC p. 75
Or???
EXPLORE!
1 – draw each of the shapes on graph paper, then draw
all of the diagonals from one vertex, and complete the
table.
Name
# of # of ‘s
sides formed

Sum of
measures
of

Sum of
measures of polygon
triangle
3
1
180
quad.
4
2
180
360
180
540
pentagon 5
3
hexagon
6
4
180
n-gon
n
n-2
180
180
720
n-2(180)
Learning Objective: to identify properties of polygons, and to find the sums of the
measures of the interior and exterior angles of polygons
Sum of interior angles of a polygon -
 n  2180
n = #of sides
Ex 1 – A barn is shaped like the polygon in the diagram.
Find the measure of each unknown angle in the diagram
x
x
x
sum   n  2180
x
x
7
 2180
sum  900
equation...
5x 180  900
5x  720
x  144
Learning Objective: to identify properties of polygons, and to find the sums of the
measures of the interior and exterior angles of polygons
Ex 2 – what polygon, if any, has angle measures that add up
to 2000º?
 n  2180  2000
n2 
118
n
9
100
9
EH…not a whole number,
so no polygon…
Learning Objective: to identify properties of polygons, and to find the sums of the
measures of the interior and exterior angles of polygons
Sum of exterior angles of a polygon –
4
3
1
3
5
1
2
Sum of exterior angles of a polygon –
360
0
Yep…always!
2
Ckc – P. 82
Out –explain how to find the sum of the
interior angles of a polygon. (ticket out!)
Summary – I think I
understand…
Or…I’m not sure about….
POW!!
HW –
p. 76 #1-4, 17-23 odd
p. 83 #1-9, 19-31 odd