A piece of string whose length is 32cm is cut into 2 pieces. one piece is used to form an equilateral triangle and the other to form of the circle so that the sum of the areas is a minimum? Find the minimum sum of the areas. Express your answer in pi. What is the function
Computation of derivative
Computation of Critical numbers
Computation of minimum value
1
Expert's answer
2022-03-21T06:43:36-0400
Solution.
Determine:
x cm - a piece is used to form an equilateral triangle.
32-x cm - a piece is used to form a circle.
S1=4a23 - the area of the triangle.
a=3x ; S1=36x23.
S2=πr2 - the area of the circle.
l=2πr ; r=2πl=2π32−x;
S2=π(2π32−x)2=4π1(32−x)2.
The sum of the areas:
S=S1+S2=36x23+4π1(32−x)2 .
Derivative of the function:
S’=362x3−2π32−x=0
362x3=2π32−x
9x3=π32−x
x0=π3+99⋅32 - critical number.
As S’’=183+2π1>0 so S(x0) is the minimum value of the function S(x).
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