Respuesta :
Answer:
S(min) = 59,66 cm²
Step-by-step explanation:
The volume of a cylindrical can is:
V(c) = π*x²*h where x is radius of the base and h the height
V(c) = 50 cm³
50 = π*x²*h (1)
The surface area of the can (Sc) is Surface area of the base (Sb) plus surface lateral area (Sl)
S(b) = π*x²
And S(l) = 2*π*x*h
Then
S(c) = π*x² + 2*π*x*h
And surface area as a function of x is
From equation (1)
h = 50 /π*x² and plugging this value in the previous expression
S(x) = π*x² + 2*π*x*(50/π*x²)
S(x) = π*x² + 100/x
Taking derivatives on both sides of the equation
S´(x) = 2*π*x - 100/x²
S´(x) = 0 means 2*π*x - 100/x² = 0
π*x - 50/x² = 0
π*x³ - 50 = 0
π*x³ = 50
x³ = 50 / 3,14
x³ = 15,92
x = 2,51 cm
And h = 50 / π* (2,51)²
h = 2,53 cm
Then minimum surface area of the can is:
S(min) = 19,78 + 39,88
S(min) = 59,66 cm²
