document.write( "Question 263596: A piece of wire 40cm long is to be cut into two pieces. One piece wil be bent to form a circle; the other will be bent to form a square. Find the lengths of the two pieces that cause the sum of the area of the circle and square to be a minimum. \n" ); document.write( "
Algebra.Com's Answer #194300 by ankor@dixie-net.com(22740)\"\" \"About 
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A piece of wire 40cm long is to be cut into two pieces.
\n" ); document.write( " One piece will be bent to form a circle; the other will be bent to form a square.
\n" ); document.write( " Find the lengths of the two pieces that cause the sum of the area of the circle and square to be a minimum.
\n" ); document.write( ":
\n" ); document.write( "Let x = circumference of the circle
\n" ); document.write( "then
\n" ); document.write( "(40-x) = perimeter of the square
\n" ); document.write( ":
\n" ); document.write( "Find the radius of the circle
\n" ); document.write( "r = \"x%2F%282pi%29\"
\n" ); document.write( "Find the area of the circle
\n" ); document.write( "a = \"pi%28x%2F%282pi%29%29%5E2+\"
\n" ); document.write( "a = \"pi%28x%5E2%2F%284pi%5E2%29%29\"
\n" ); document.write( "Cancel pi
\n" ); document.write( "a = \"x%5E2%2F%284pi%29\"
\n" ); document.write( ":
\n" ); document.write( "Find the area of the square:
\n" ); document.write( "a = \"%28%2840-x%29%2F4%29%5E2\"
\n" ); document.write( "a = \"%28x%5E2+-+80x+%2B+1600%29%2F16\"
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "Total area
\n" ); document.write( "A = \"x%5E2%2F%284pi%29\" + \"%28x%5E2+-+80x+%2B+1600%29%2F16\"
\n" ); document.write( "Change to decimals, easier to combine like terms
\n" ); document.write( "A = .07958x^2 + .0625x^2 - 5x + 100
\n" ); document.write( "A = .14208x^2 - 5x + 100
\n" ); document.write( ":
\n" ); document.write( "Find the axis of symmetry [x = -b/(2a)]
\n" ); document.write( "x = \"%28-%28-5%29%29%2F%282%2A.14208%29\"
\n" ); document.write( "x = \"5%2F.28416\"
\n" ); document.write( "x ~ 17.6 inches, the piece of wire creating a circle
\n" ); document.write( "and
\n" ); document.write( "40 - 17.6 = 22.4 inches, the piece of wire creating the square
\n" ); document.write( ":
\n" ); document.write( "These lengths should give minimum area of the circle and square together
\n" ); document.write( "
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