Math Problem Statement

A company designs a logo by drawing two identical circles of radius 10 cm whose centers are placed 16 cm apart. The logo is then formed using the shaded region shown in the diagram. Find the area of the shaded region.

Solution

To solve the problem of finding the area of the shaded region in the diagram, let's break it down step-by-step:

Step 1: Understand the Geometry

The shaded region is the intersection of two identical circles with radii r=10cmr = 10 \, \text{cm}, whose centers are 16cm16 \, \text{cm} apart.

The area of the shaded region (intersection) can be calculated as the area of two circle segments. Each segment is part of a circle that lies on either side of the line joining the two circle centers.

Step 2: Segment Area Formula

The area of a segment of a circle is given by: Segment Area=r2cos1(d2r)d24r2d2\text{Segment Area} = r^2 \cos^{-1}\left(\frac{d}{2r}\right) - \frac{d}{2} \sqrt{4r^2 - d^2} where:

  • rr is the radius of the circle (10cm10 \, \text{cm}),
  • dd is the distance between the centers of the circles (16cm16 \, \text{cm}).

Step 3: Calculate One Segment Area

Let us substitute r=10cmr = 10 \, \text{cm} and d=16cmd = 16 \, \text{cm} into the formula:

  1. Calculate cos1(d2r)\cos^{-1}\left(\frac{d}{2r}\right): cos1(d2r)=cos1(1620)=cos1(0.8)\cos^{-1}\left(\frac{d}{2r}\right) = \cos^{-1}\left(\frac{16}{20}\right) = \cos^{-1}(0.8) Using a calculator or reference, cos1(0.8)0.6435radians\cos^{-1}(0.8) \approx 0.6435 \, \text{radians}.

  2. Calculate the term d24r2d2\frac{d}{2} \sqrt{4r^2 - d^2}: d2=162=8\frac{d}{2} = \frac{16}{2} = 8 4r2d2=4(10)2162=400256=144=12\sqrt{4r^2 - d^2} = \sqrt{4(10)^2 - 16^2} = \sqrt{400 - 256} = \sqrt{144} = 12 So: d24r2d2=8×12=96\frac{d}{2} \sqrt{4r^2 - d^2} = 8 \times 12 = 96

  3. Segment area for one circle: Segment Area=102×0.643596=100×0.643596=64.3596=28.35cm2\text{Segment Area} = 10^2 \times 0.6435 - 96 = 100 \times 0.6435 - 96 = 64.35 - 96 = 28.35 \, \text{cm}^2

Step 4: Total Intersection Area

Since there are two identical circle segments contributing to the intersection: Total Shaded Area=2×28.35=56.7cm2\text{Total Shaded Area} = 2 \times 28.35 = 56.7 \, \text{cm}^2

Final Answer:

The area of the shaded region is: 56.7cm2\boxed{56.7 \, \text{cm}^2}

Would you like a detailed explanation of any step or visual representation? Here are related questions for further exploration:

  1. How does the segment area formula account for both arc and triangular portions?
  2. Can the shaded area be derived using integration instead of geometry?
  3. What happens if the circle centers are closer or farther than 16 cm?
  4. How can the formula be generalized for circles of different radii?
  5. How can approximations affect the result in practical applications?

Tip: Always double-check the angle in radians when working with trigonometric functions, as incorrect units can lead to errors.

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Math Problem Analysis

Mathematical Concepts

Geometry
Area of a Circle
Circle Segment
Intersection of Circles

Formulas

Segment Area = r^2 * cos^(-1)(d / 2r) - (d / 2) * sqrt(4r^2 - d^2)
Total Shaded Area = 2 * Segment Area

Theorems

Pythagoras' Theorem for finding segment dimensions
Trigonometric relationships for arc angles

Suitable Grade Level

Grades 10-12