If an interior angle of a regular polygon measures 144°, how many sides does the polygon have?

1 answer

To determine the number of sides in a regular polygon given that the measure of each interior angle is \(144^\circ\), we can use the formula for the measure of an interior angle of a regular polygon:

\[ \text{Interior angle} = \frac{(n-2) \times 180^\circ}{n} \]

where \(n\) is the number of sides of the polygon.

Given that the interior angle is \(144^\circ\), we set up the equation:

\[ \frac{(n-2) \times 180}{n} = 144 \]

First, we multiply both sides of the equation by \(n\) to eliminate the fraction:

\[ (n - 2) \times 180 = 144n \]

Next, we expand the left side:

\[ 180n - 360 = 144n \]

Now, we subtract \(144n\) from both sides to combine like terms:

\[ 180n - 144n - 360 = 0 \]

This simplifies to:

\[ 36n - 360 = 0 \]

Next, we add \(360\) to both sides:

\[ 36n = 360 \]

Now, divide both sides by \(36\):

\[ n = \frac{360}{36} = 10 \]

Thus, the number of sides in the polygon is \( \boxed{10} \).

To verify, we can calculate the interior angle for a 10-sided polygon (decagon):

  1. Calculate the total interior angles using the formula \( (n-2) \times 180 \):

\[ (10 - 2) \times 180 = 8 \times 180 = 1440^\circ \]

  1. Calculate the measure of each interior angle:

\[ \frac{1440}{10} = 144^\circ \]

This confirms that our calculation was correct, and the polygon is indeed a decagon with \( \boxed{10} \) sides.