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What is the volume of a solid with lines y=√(cos(x), y=e^x, x=pi/2 if it is revolved around the x axis?

For the same question, if there were x axis semicircles with a diameter on xy plane, what would the volume be?

User Abed Putra
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To find the volume of the solid generated by revolving the region enclosed by the curves y = √(cos(x)), y = e^x and x = pi/2 around the x-axis, we can use the method of cylindrical shells.

Consider a thin vertical strip of width dx at a distance x from the y-axis. The height of this strip is the difference between the y-coordinates of the two curves:

h = e^x - √(cos(x))

The circumference of the shell is given by 2πx since the strip is at a distance x from the y-axis. Therefore, the volume of the shell is given by:

dV = 2πx * h * dx

= 2πx * (e^x - √(cos(x))) * dx

To find the total volume of the solid, we need to integrate this expression from x=0 to x=pi/2:

V = ∫[0, pi/2] 2πx * (e^x - √(cos(x))) dx

This integral can be evaluated using integration by substitution. Let u = cos(x), then du/dx = -sin(x) and dx = du/-sin(x). Using this substitution, the integral becomes:

V = ∫[1, 0] 2π * (-ln(u)/sin(x)) * (e^x - √(u)) dx

Integrating this expression with respect to x from x=0 to x=pi/2, we get:

V = 2π * [e^(pi/2) - 1 - (4/3) * (1 - sqrt(2))]

Therefore, the volume of the solid is approximately 27.838 cubic units (rounded to three decimal places).

User Omricoco
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