Interior and Exterior Angle of a Polygon: Formula not working

In summary, to find the number of sides of a polygon given the measure of each interior angle is 8 times the measure of each exterior angle, we can use the equation ((n-2) * 180)/n = 8 * (360)/n. Solving for n, we get n = 18 as the answer.
  • #1
zak100
462
11

Homework Statement


How many sides does a polygon have if the measure of each interior angle is 8 times the measure of each exterior angle?

Homework Equations


Interior angle of a polygon: ((n-2) * 180)/n
Exterior angle of a polygon: (360)/n

The Attempt at a Solution


((n-2) * 180)/n = 8 * (360)/n
now ((n-2) * 180) = 8 * 360
180 n -360 = 8 * 360
180 n = 7 * 360
n = 14
I am getting n = 14 which is wrong.

Some body please guide me what is the problem.

Zulfi.
 
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  • #2
zak100 said:

Homework Statement


How many sides does a polygon have if the measure of each interior angle is 8 times the measure of each exterior angle?

Homework Equations


Interior angle of a polygon: ((n-2) * 180)/n
Exterior angle of a polygon: (360)/n

The Attempt at a Solution


((n-2) * 180)/n = 8 * (360)/n
now ((n-2) * 180) = 8 * 360
180 n -360 = 8 * 360
Work is fine to here, but you have a mistake in the line below. Two lines above, it would be simpler to divide both sides by 180, to get simpler numbers to work with.
Alternatively, in the line above, you are adding 360 to both sides of the equation.
zak100 said:
180 n = 7 * 360
n = 14
I am getting n = 14 which is wrong.

Some body please guide me what is the problem.

Zulfi.
 
  • #3
zak100 said:
180 n -360 = 8 * 360
180 n = 7 * 360

Check the math

EDIT: beaten for some seconds by Mark44
 
Last edited:

1. What is the formula for finding the interior and exterior angles of a polygon?

The formula for finding the interior angle of a regular polygon is (n-2) x 180 / n, where n is the number of sides. The formula for finding the exterior angle of a regular polygon is 360 / n.

2. Why is the formula not working for my polygon?

The formula only works for regular polygons, meaning all sides and angles are equal. If your polygon is irregular, the formula will not apply and you will need to use a different method to find the interior and exterior angles.

3. Can the formula be used for all types of polygons?

No, the formula is only applicable for regular polygons. For irregular polygons, the sum of the interior angles can still be found using the formula (n-2) x 180, but individual angles cannot be determined using this formula.

4. How do I find the interior and exterior angles of a polygon if I know the number of sides?

If you know the number of sides of a regular polygon, you can use the formulas mentioned in the first question to find the interior and exterior angles.

5. Are there any other methods for finding the interior and exterior angles of a polygon?

Yes, there are other methods such as using trigonometry or dividing the polygon into triangles. These methods can be used for both regular and irregular polygons.

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