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1. A circle is inscribed in a square as shown in the figure below. The circumference of the circle is

increasing at a constant rate of 6 inches per second. As the circle expands, the square expands to
maintain the condition of tangency.
(Note: A circle with radius r has circumference C = 2лr and area A = πr².)
a)
b)
Find the rate at which the perimeter of the square is increasing. Indicate units of measure.
At the instant when the area of the circle is 257 square inches, find the rate of increase in the
area enclosed between the circle and the square. Indicate units of measure.

1. A circle is inscribed in a square as shown in the figure below. The circumference-example-1
User Brajeshwar
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1 Answer

4 votes

Answer:

Explanation:

Let's name the radius of the circle "r". Because the circumference of the circle grows at a constant rate of 6 inches per second, we can apply the calculation C = 2 * pi * r to calculate the rate at which the radius grows.

dC/dt = 2 * pi * dr/dt = 6 inches/second

Because the square is parallel to the circle, the length of one of its sides equals the diameter of the circle. As a result, the square's perimeter equals four times the diameter of the circle or P = 4 * 2 * r.

As a result, the pace at which the square's perimeter grows is:

dP/dt equals 4 * 2 * dr/dt equals 8 * dr/dt

Substituting the dr/dt value from the first equation:

dP/dt = 8 * dC/dt = 8 * 6 inches per second = 48 inches per second

The pace at which the perimeter of the square is growing is 48 inches/second

b) The circle's area is determined by A = pi * r2.

If A = 257 square inches, we may calculate the value of r at that moment.

sqrt(A/pi) = sqrt(257/pi)

The rate of growth in the circle area is dA/dt = 2 * pi * r * dr/dt.

Substituting the dr/dt value from the first equation and the r value from above:

dA/dt = 2 pi * sqrt(257/pi) * 6 in/sec = 12 sqrt(257) in/sec

The area enclosed between the circle and the square equals the square's area minus the circle's area.

Let's call the square's side length s.

enclosed area = s2 - A = s2 - pi * r2

d(s2 - pi * r2)/dt = 2sds/dt is the rate of expansion of the enclosed area.

We may calculate the rate of increase of the enclosed area by substituting the value of ds/dt from the first equation.

ds/dt = dP/dt / 4 = 48 inches per second / 4 = 12 inches per second

d(s^2 - pi * r^2)

/dt = 2 * s * ds/dt = 2 * s * 12 inches/sec = 24 * s

The rate of expansion in the area enclosed between the circle and the square is 24*s inches/sec at the instant when the size of the circle is 257 square inches.

Please note that s is not supplied in the issue, thus it's impossible to determine the precise value of the rate of increase in the area contained.

User Gunavant Patel
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