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7-5 Angles and Polygons
P. 324
To find the name of common polygons please refer to page 324.
POLYGON- A figure with 3 or more sides
To find the sum of the measure of the interior angles is IA= (N-2)180
N represents the number of sides
To find the sum of the Interior angles you would use the
following: IA=(4-2)180=360
You take 4 because there are four sides and you subtract two
and multiply by 180.
If you are given a side with 7 sides then you would put it into the formula (7-2)180= 900
A regular polygon means that all the angles are equal so if you are given a formula you insert the
number of sides then divide by the number of sides.
For example is you are told that you have a regular Nonagon (9) sides you would do the following
(9-2)180=1260
then 1260/9=140 meaning that all 9 angles have 140 degrees.
You can also use the formula to find an unknown degree of an angle. Use the formula to find the total
of the figure then subtract the total degrees you currently have.