1.8, Problem 37: A lidless cardboard box is to be made with a volume of 4 m3
. Find the
dimensions of the box that requires the least amount of cardboard.
Solution: If the dimensions of our box are x, y, and z, then we’re seeking to minimize
A(x, y, z) = xy + 2xz + 2yz subject to the constraint that xyz = 4. Our first step is to make
the first function a function of just 2 variables. From xyz = 4, we see z = 4/xy, and if we substitute
this into A(x, y, z), we obtain a new function A(x, y) = xy + 8/y + 8/x. Since we’re optimizing
something, we want to calculate the critical points, which occur when Ax = Ay = 0 or either Ax
or Ay is undefined. If Ax or Ay is undefined, then x = 0 or y = 0, which means xyz = 4 can’t
hold. So, we calculate when Ax = 0 = Ay. Ax = y − 8/x2 = 0 and Ay = x − 8/y2 = 0. From
these, we obtain x
2y = 8 = xy2
. This forces x = y = 2, which forces z = 1. Calculating second
derivatives and applying the second derivative test, we see that (x, y) = (2, 2) is a local minimum
for A(x, y). To show it’s an absolute minimum, first notice that A(x, y) is defined for all choices
of x and y that are positive (if x and y are arbitrarily large, you can still make z REALLY small
so that xyz = 4 still). Therefore, the domain is NOT a closed and bounded region (it’s neither
closed nor bounded), so you can’t apply the Extreme Value Theorem. However, you can salvage
something: observe what happens to A(x, y) as x → 0, as y → 0, as x → ∞, and y → ∞. In each
of these cases, at least one of the variables must go to ∞, meaning that A(x, y) goes to ∞. Thus,
moving away from (2, 2) forces A(x, y) to increase, and so (2, 2) is an absolute minimum for A(x, y).
Answer:
36π
Step-by-step explanation:
The area of a circle is given as:
where r = radius of the circle
The area of a sector of a circle is given as:
where α = central angle in radians
Since 
is the area of a circle, A, this implies that:
A circle has a sector with area 33 pi and a central angle of 11/6 pi radians.
Therefore, the area of the circle, A, is:
The area of the circle is 36π.
Answer:
The next number selected should be between 2 and 3 .
Step-by-step explanation:
x. x f(x) g(x)
0 10 17
1 11 19
2 14 21
3 19 23
4 26 25
3.5 22.25 24
<u>2.5 16.25 22</u>
1.5 12.25 20
0.5 10.25 18
We see the pattern that it is increasing with only a unit. The last given data is mid of the last two values that is 3 and 4.
So the next value would be the mid of the next last two values that is 2 and 3 and will be 2.5
Now it is moving in the reverse direction in the same pattern with a difference of a unit.
