Math Problem Statement

he area of the shaded sector is shown. Find the radius of $\odot M$ . Round your answer to the nearest hundredth.

A circle with center at point M. Two points K and J are marked on the circle such that the measure of the angle corresponding to minor arc K J, at the center, is 89 degrees. Point L is marked on major arc K J. Area of minor sector is equal to 12.36 square meters.

The radius is about meters.

Solution

We can find the radius of the circle using the formula for the area of a sector. The area AA of a sector is given by the formula:

A=θ360×πr2A = \frac{\theta}{360^\circ} \times \pi r^2

Where:

  • AA is the area of the sector,
  • θ\theta is the central angle in degrees,
  • rr is the radius of the circle.

From the problem:

  • The area of the sector A=12.36A = 12.36 square meters,
  • The central angle θ=89\theta = 89^\circ.

Substitute these values into the formula:

12.36=89360×πr212.36 = \frac{89^\circ}{360^\circ} \times \pi r^2

Now, solve for rr:

  1. Multiply both sides by 360360^\circ to eliminate the denominator:

12.36×360=89×πr212.36 \times 360 = 89^\circ \times \pi r^2

  1. Simplify:

4449.6=89×πr24449.6 = 89^\circ \times \pi r^2

  1. Divide both sides by 89π89^\circ \pi:

r2=4449.689×πr^2 = \frac{4449.6}{89^\circ \times \pi}

  1. Calculate the denominator 89×π89^\circ \times \pi:

89×π89×3.1416=279.06489^\circ \times \pi \approx 89 \times 3.1416 = 279.064

r2=4449.6279.06415.94r^2 = \frac{4449.6}{279.064} \approx 15.94

  1. Finally, take the square root to find rr:

r15.943.99metersr \approx \sqrt{15.94} \approx 3.99 \, \text{meters}

So, the radius of the circle is approximately 3.99 meters.

Would you like further clarification or details on the solution? Here are some related questions you might find helpful:

  1. How would the radius change if the angle were different?
  2. What is the formula for the area of a sector of a circle?
  3. How do you find the area of the sector when you know the arc length instead of the central angle?
  4. What other methods can be used to calculate the radius of a circle if the area of the sector is given?
  5. How does the size of the central angle affect the area of the sector?

Tip: When dealing with sectors and angles, always make sure that your angle is in the correct units (degrees or radians) and that you use the correct formula for the area.

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Math Problem Analysis

Mathematical Concepts

Geometry
Circles
Sector Area
Radius Calculation

Formulas

A = (θ / 360) * π * r²

Theorems

Sector Area Formula

Suitable Grade Level

Grades 8-10