SOLUTION: a rectangle has area 100 ft^2. Find the dimensions of the rectangle that would minimize the length of the diagonal of the rectangle. There should be 2 dimensions

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Question 880956: a rectangle has area 100 ft^2. Find the dimensions of the rectangle that would minimize the length of the diagonal of the rectangle. There should be 2 dimensions
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
The area of a rectangle is
A=L%2AW=100
The diagonal of a rectangle is,
D%5E2=L%5E2%2BW%5E2
From the area,
L=100%2FW
L%5E2=10000%2FW%5E2
Substituting
D%5E2=10000%2FW%5E2%2BW%5E2
Differentiating with respect to W,
2D%2A%28dD%2FdW%29=-20000%2FW%5E3%2B2W
Set the derivative equal to zero to get the minimum distance.
dD%2FdW=%28-20000%2FW%5E3%2B2W%29%2F2D=0
20000%2FW%5E3=2W
W%5E4=10000
W=10
Then,
L=100%2FW
L=10
The shortest diagonal occurs when the rectangle is actually a square.