The radius of a circle is 3 miles. What is the length of a 180° arc? -3 mi 180° Give the exact answer in simplest form.

Elementary Geometry For College Students, 7e
7th Edition
ISBN:9781337614085
Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
Publisher:Alexander, Daniel C.; Koeberlein, Geralyn M.
ChapterP: Preliminary Concepts
SectionP.CT: Test
Problem 1CT
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The formula for the length of an arc is given by:

\[ l = \frac{m}{360} \cdot C \]

where \( l \) is the arc length, \( C \) is the circumference, and \( m \) is the measure of the arc in degrees.

The arc's length depends on the arc's measure and the circle's circumference. You already know that the arc's measure is 135°, so find the circle's circumference.

**First, find the circumference:**

\[ C = 2\pi r \]

\[ = 2\pi (3) \quad \text{Plug in } r = 3 \]

\[ = 6\pi \quad \text{Multiply} \]

The circumference is \( 6\pi \) centimeters.

**Now, find the length of the arc:**

\[ l = C \cdot \frac{m}{360} \]

\[ = 6\pi \cdot \frac{135}{360} \quad \text{Plug in } C = 6\pi \text{ and } m = 135 \]

\[ = \frac{9\pi}{4} \quad \text{Multiply and simplify} \]

The length of the arc is \( \frac{9\pi}{4} \) centimeters.
Transcribed Image Text:The formula for the length of an arc is given by: \[ l = \frac{m}{360} \cdot C \] where \( l \) is the arc length, \( C \) is the circumference, and \( m \) is the measure of the arc in degrees. The arc's length depends on the arc's measure and the circle's circumference. You already know that the arc's measure is 135°, so find the circle's circumference. **First, find the circumference:** \[ C = 2\pi r \] \[ = 2\pi (3) \quad \text{Plug in } r = 3 \] \[ = 6\pi \quad \text{Multiply} \] The circumference is \( 6\pi \) centimeters. **Now, find the length of the arc:** \[ l = C \cdot \frac{m}{360} \] \[ = 6\pi \cdot \frac{135}{360} \quad \text{Plug in } C = 6\pi \text{ and } m = 135 \] \[ = \frac{9\pi}{4} \quad \text{Multiply and simplify} \] The length of the arc is \( \frac{9\pi}{4} \) centimeters.
**Understanding Arc Length**

**Problem Statement:**
The radius of a circle is 3 miles. What is the length of a 180° arc?

**Diagram Explanation:**
The provided diagram represents a circle with a radius (r) of 3 miles. The diagram highlights a 180° arc, which is half of the circle's circumference.

**Steps to Solve:**

1. **Identify the formula for the circumference of a circle:**
   \[
   \text{Circumference} = 2 \pi r
   \]

2. **Substitute the given radius into the formula:**
   \[
   \text{Circumference} = 2 \pi \times 3 \text{ miles} = 6 \pi \text{ miles}
   \]

3. **Understand that the 180° arc is half of the full circle's circumference.**

4. **Calculate the arc length:**
   \[
   \text{Arc Length} = \frac{180^\circ}{360^\circ} \times \text{Circumference}
   \]
   \[
   \text{Arc Length} = \frac{1}{2} \times 6 \pi \text{ miles} = 3 \pi \text{ miles}
   \]

**Answer:**
The length of a 180° arc is \( 3 \pi \) miles.

Please provide your final answer in the input box:

**Answer:**
\( \_\_\_\_\_\_\_\_ \text{ miles} \)
Transcribed Image Text:**Understanding Arc Length** **Problem Statement:** The radius of a circle is 3 miles. What is the length of a 180° arc? **Diagram Explanation:** The provided diagram represents a circle with a radius (r) of 3 miles. The diagram highlights a 180° arc, which is half of the circle's circumference. **Steps to Solve:** 1. **Identify the formula for the circumference of a circle:** \[ \text{Circumference} = 2 \pi r \] 2. **Substitute the given radius into the formula:** \[ \text{Circumference} = 2 \pi \times 3 \text{ miles} = 6 \pi \text{ miles} \] 3. **Understand that the 180° arc is half of the full circle's circumference.** 4. **Calculate the arc length:** \[ \text{Arc Length} = \frac{180^\circ}{360^\circ} \times \text{Circumference} \] \[ \text{Arc Length} = \frac{1}{2} \times 6 \pi \text{ miles} = 3 \pi \text{ miles} \] **Answer:** The length of a 180° arc is \( 3 \pi \) miles. Please provide your final answer in the input box: **Answer:** \( \_\_\_\_\_\_\_\_ \text{ miles} \)
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