The price of a large can of fancy popcorn is $8.17. Between which two prices is the price of the popcorn?
2 answers:
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Answer:
7. d. l = 6.48 cm, w = 6.48 cm
8. d. square
Step-by-step explanation:
For a given area, the perimeter can always be shortened by reducing the length of the long side and increasing the length of the short side. When you get to the point where you can't do that, then you have the minimum perimeter. You will reach that point when the sides are the same length: the rectangle is a square.
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7. In light of the above, the best dimensions are √42 ≈ 6.48 cm for length and width.
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8. In light of the above, the shape is a square.
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The attached graph shows the length of one side (x) and the associated perimeter. The other side is 42/x, which will also be 6.48.
Replace x with π/2 - x to get the equivalent integral
but the integrand is even, so this is really just
Substitute x = 1/2 arccot(u/2), which transforms the integral to
There are lots of ways to compute this. What I did was to consider the complex contour integral
where γ is a semicircle in the complex plane with its diameter joining (-R, 0) and (R, 0) on the real axis. A bound for the integral over the arc of the circle is estimated to be
which vanishes as R goes to ∞. Then by the residue theorem, we have in the limit
and it follows that