95. A wire of length 28 m is to be cut into two pieces. One of the pieces is to be made into a square and the other into a circle. What should be the length of the two pieces so that the combined area of the square and the circle is minimum?

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9 months ago

Let x and y in 'm' be the length of side of the square the radius of the circle respectily

Then, length of wire = perimeter of square + circumference of circle

28 = 4x + 2πy

 2x + πy = 14

y=142xx

The combine area A of the square and the circle is

A = x2 + πy2

=x2+π[142xπ]2

=x2+[2(7x)x]2

=x2+4π(7x)2.

So, dAdx=2x+42π(7x)+(1)=2x8π(7x)

d2Adx2=2+8π

At, dAdx=0

2x8(7x)π=0

2x=8π(7x)

2πx=568x

(2x+8)x=56

x=562π+8=28x+4.

At, x=28π+4,d2Adx2=2+γπ>0

x=28π+4 isa point of minima

Hence, length of squa

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