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Set up an integral for the volume of the solid obtained by rotating the region bounded by the given curves about the specified line. Then use your calculator to evaluate the integral correct to five decimal places. y = e−x^2, y = 0, x = −2, x = 2​

Sagot :

Y = 4x*e^(-x) , y=0, x=3 , rotation about y-axis
Graph or sketch the function.
The volumeelement is a cylinder with radius x height y and thickness dx.
Integrate from x=0 to x=3
V = 2 π ∫x*y dx =
2 π ∫x*4x*e^(-x) dx
8 π ∫x²*e^(-x) dx ,
Integrate by part: ∫e^(-x)*x² dx , let u’ = e^(-x) => u = -e^(-x) and v = x² => v’ = 2x
∫e^(-x)*x² dx = -e^(-x)*x² + ∫e^(-x)*2x dx
Integrate by part: ∫e^(-x)*2x dx = -e^(-x)*2x + ∫e^(-x)*2 dx
∫2e^(-x) dx = -2e^(-x).
If we wrap up the above we get :
V = 8 π*[-e^(-x)*(x²+2x+2)]
V = 8 π*[e⁻³(9+6+2) – (-e⁰ *2)]
V = 8 π*[17*e⁻³+ 2] = 28.99363 v.u.