Answer:
(a)I. 13 Sides II. 7 Sides
(b) 4 Sides, Square
(c)x=52 degrees
(d)x=107 degrees
(e)1620 degrees
Step-by-step explanation:
(a)The Sum of the Interior angle of polygon with n sides is derived using the formula: (n-2)180.
I. If the Interior angle is ![1980^0](https://tex.z-dn.net/?f=1980%5E0)
Then:
![(n-2)180^0=1980^0\\$Divide both sides by 180^0 $ to isolate n$\\n-2=11\\$Add 2 to both sides of the equation\\n-2+2=11+2\\n=13](https://tex.z-dn.net/?f=%28n-2%29180%5E0%3D1980%5E0%5C%5C%24Divide%20both%20sides%20by%20180%5E0%20%24%20to%20isolate%20n%24%5C%5Cn-2%3D11%5C%5C%24Add%202%20to%20both%20sides%20of%20the%20equation%5C%5Cn-2%2B2%3D11%2B2%5C%5Cn%3D13)
The polygon has <u>13 sides.</u>
II. If the Interior angle is ![900^0](https://tex.z-dn.net/?f=900%5E0)
Then:
![(n-2)180^0=900^0\\$Divide both sides by 180^0 $ to isolate n$\\n-2=5\\$Add 2 to both sides of the equation\\n-2+2=5+2\\n=7](https://tex.z-dn.net/?f=%28n-2%29180%5E0%3D900%5E0%5C%5C%24Divide%20both%20sides%20by%20180%5E0%20%24%20to%20isolate%20n%24%5C%5Cn-2%3D5%5C%5C%24Add%202%20to%20both%20sides%20of%20the%20equation%5C%5Cn-2%2B2%3D5%2B2%5C%5Cn%3D7)
The polygon has <u>7 sides.</u>
(b)The sum of the exterior angle of a polygon is 360 degrees,
Each exterior angle of a n-sided regular polygon is: ![\frac{360^0}{n}](https://tex.z-dn.net/?f=%5Cfrac%7B360%5E0%7D%7Bn%7D)
If the exterior angle of a regular polygon is 90°
Then:
![90\°=\frac{360^0}{n}\\ 90n=360\\n=4](https://tex.z-dn.net/?f=90%5C%C2%B0%3D%5Cfrac%7B360%5E0%7D%7Bn%7D%5C%5C%2090n%3D360%5C%5Cn%3D4)
The regular polygon has 4 sides and it is called a <u>Square.</u>
<u>(c)</u>The Sum of the Interior angle of polygon with n sides is derived using the formula: (n-2)180.
Each Interior angle of a regular n-sided polygon is: ![\frac{(n-2)180^0}{n}](https://tex.z-dn.net/?f=%5Cfrac%7B%28n-2%29180%5E0%7D%7Bn%7D)
For a pentagon, n=5
Then:
![\frac{(5-2)180^0}{5}=2x+4\\108=2x+4\\108-4=2x\\104=2x\\x=52^0](https://tex.z-dn.net/?f=%5Cfrac%7B%285-2%29180%5E0%7D%7B5%7D%3D2x%2B4%5C%5C108%3D2x%2B4%5C%5C108-4%3D2x%5C%5C104%3D2x%5C%5Cx%3D52%5E0)
(d)The <u>sum of the exterior angle of a polygon is 360 degrees.</u>
If four of the exterior angles of a pentagon are 57, 74, 56, and 66.
Let the fifth angle=x
Then:
![57+74+56+66+x=360^0\\253+x=360\\x=107^0](https://tex.z-dn.net/?f=57%2B74%2B56%2B66%2Bx%3D360%5E0%5C%5C253%2Bx%3D360%5C%5Cx%3D107%5E0)
(e)The Sum of the Interior angle of polygon with n sides is derived using the formula: (n-2)180.
In an 11-gon., n=11
Therefore, the sum of the interior angle=(11-2)180=![1620^0](https://tex.z-dn.net/?f=1620%5E0)
The sum of the interior angle <u>does not change either in a regular or irregular polygon.</u>