Practical application of derivative (optimization problem in life)! When the volume of cylindrical metal beverage can is certain, how to choose its height and radius in order to save the materials?

Practical application of derivative (optimization problem in life)! When the volume of cylindrical metal beverage can is certain, how to choose its height and radius in order to save the materials?

Let the height h, radius r, v = h π R ^ 2, H = V / (π R ^ 2), the sum of the upper and lower areas is S1 = 2 π R ^ 2, the side area S2 = 2 π RH s = S1 + S2 = 2 π RH + 2 π R ^ 2 = 2V / R + 2 π R ^ 2 s' = - 2V / R ^ 2 + 4 π R, and the maximum value is s' = 0, v = 4 π R ^ 3, so h = 4R

If you want to make an open cylindrical container with a volume of 8 π, ask the bottom radius and height to save the most materials

let r be the radiush be the heightV= πr^2h = 8πh=8/r^2A = πr^2 + 2πrh= πr^2 + 16π/rA' =π(2r-16/r^2)=02r^3-16=0r=2A'' =π(2+32/r^3)A''(2)>0 ( min )min A at r =2h=8/r^2= 2

1、 U = 2x + 2Y + XY + 8 find u derivative x derivative y derivative 2、 U = 2 (x square) y find u derivative x derivative y derivative

(1)du/dx=2+y
du/dy=2+x
(2)du/dx=4xy
du/dy=2x ²

Y = the derivative of F (- x), then the derivative of Y is

Solution y = f (- x)
Then y '= [f (- x)]' = f '(- x)' = - f '(x)

The n-th derivative of arcsinx First find the first derivative, square both sides, and then find the N-2 derivative of the formula after square. What is the specific process of calculating with Leibniz formula according to this method

After the derivative is squared, the result is: 1 / (1-x ^ 2) = 1 / (1-x) * (1 + x); Split item: = 1 / 2 * (1 / 1-x + 1 / 1 + x); Then I believe you can see that the problem is transformed into finding the N-2 derivative of 1 / 1-x and 1 / 1 + X, which are regular and formula; For example: {1 / 1 + X} [n-2] = (- 1) ^ n-2 * (n-2)/ (1+...

How to find the derivative of polar coordinate equation? If Without transforming it into a rectangular coordinate equation thank you

The polar coordinate equation has two parameters: the module length R and the spoke angle T. therefore, the derivation of the polar coordinate equation r = R (T) is the same as the derivation process and method in the rectangular coordinate system, that is, the derivation of R from T. only the meaning of this derivative is different, which refers to the change rate of the module length R with respect to the spoke angle t