Math Problem Statement

If the radius of a circle is 7 cm and the arc length AB is 11 cm, find the measure of the central angle ∠AOB in degrees.

Solution

We are given a circle with:

  • Radius r=7cmr = 7 \, \text{cm}
  • Arc length AB=11cmAB = 11 \, \text{cm}

The task is to find the central angle AOB\angle AOB in degrees.

We can use the formula for arc length ss to relate the arc and the angle:

s=rθs = r \theta

where:

  • ss is the arc length,
  • rr is the radius,
  • θ\theta is the angle in radians.

First, solve for θ\theta:

θ=sr=11cm7cm=1.5714radians\theta = \frac{s}{r} = \frac{11 \, \text{cm}}{7 \, \text{cm}} = 1.5714 \, \text{radians}

To convert radians to degrees:

θdegrees=θ×180π1.5714×1803.141690\theta_{\text{degrees}} = \theta \times \frac{180^\circ}{\pi} \approx 1.5714 \times \frac{180^\circ}{3.1416} \approx 90^\circ

Thus, the central angle AOB\angle AOB is approximately 9090^\circ.

Let me know if you'd like more details or have any questions!

Here are 5 related questions you might want to explore:

  1. How would the angle change if the arc length were longer or shorter?
  2. Can you derive the formula for the circumference of a circle using this concept?
  3. How would you calculate the area of the sector subtended by AOB\angle AOB?
  4. What would the arc length be if AOB\angle AOB were 4545^\circ?
  5. How would you find the length of chord ABAB?

Tip: Remember that arc length directly depends on both the radius and the angle, so increasing either will increase the arc's length.

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Math Problem Analysis

Mathematical Concepts

Geometry
Circle Theorems
Radians to Degrees Conversion

Formulas

Arc length formula: s = rθ
Radians to degrees conversion: θ(degrees) = θ(radians) × (180° / π)

Theorems

Arc length theorem in circles

Suitable Grade Level

Grades 9-10