Unit 5 Notes #2 – Exterior Angles
INTERIOR ANGLES OF A
REGULAR DODECAGON ( 12 – gon )
We use the letter _________ to
represent the NUMBER OF SIDES of a
polygon.
The NUMBER OF TRIANGLES that a
polygon with “n” sides can be divided
into using diagonals from a single vertex
is:
The SUM OF THE MEASURES OF
THE INTERIOR ANGLES of a polygon
with “n” sides is:
The measure of an INTERIOR ANGLE
of a regular polygon with “n” sides is
EXTERIOR ANGLES OF A
REGULAR DODECAGON (12 – gon )
The SUM OF THE EXTERIOR
ANGLES of any polygon is:
The MEASURE OF AN EXTERIOR
ANGLE of a regular polygon with “n”
sides is
Number
of Sides
3
4
5
6
7
8
9
10
180
360
540
720
900
1080
1260
1440
Interior
angle for
regular
polygon
60
90
108
Exterior
angle for
regular
polygon
120
Sum of
interior
Angles
Richard Sudo
Friday, February 26, 2016 4:01:45 PM CT
128.57
60
00:19:e3:4a:d2:21
144
45
40
11
12
Example problems:
What if you know some of the INTERIOR angles of a polygon
but you need to find a “missing” angle ? (Hint: start with what
the total is and subtract the ones you know. You may have to
find some angles using linear pairs, vertical angles, etc.)
What if you know some of the EXTERIOR angles of a polygon but you
need to find a “missing angle” (Hint: start with 360 – the exterior
angles always add up to 360 no matter what kind of polygon – and
subtract from there).
What if you know the sum of the measures of the INTERIOR angles and you need to find the number of sides?
(Hint: Use 180 (n –2) = the sum and figure out what “n” is by guessing or by solving.
How many sides does a polygon have
if the sum of its interior angles
is 34200 ?
What if you know what one of the INTERIOR angles of a regular polygon is and you need to find the number
of sides? (Hint: Use (180(n – 2) ) / n = the angle and figure out what “n” is by guessing or by solving.
How many sides does a regular
polygon have if the measure
of one of its interior angles is 1620 ?
What if you know what one of the EXTERIOR angles of a regular polygon is and you need to find the number
of sides? ( Hint: Use 360/n = exterior angle and figure out what “n” is by guessing or by solving.
How many sides does a regular
polygon have if the measure of
one of its exterior angles is 150 ?
Richard Sudo
Friday, February 26, 2016 4:01:45 PM CT
00:19:e3:4a:d2:21