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Ch. 8 - Techniques of Integration
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Non è quello che usi tu?Cambia libro di testo
Capitolo 8, Problema 8.2.64b

Consider the region bounded by the graphs of
y = arctan(x), y = 0, and x = 1.
b. Find the volume of the solid formed by revolving this region about the y-axis.

Guida verificata passo dopo passo
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First, identify the region bounded by the curves: \(y = \arctan(x)\), \(y = 0\), and the vertical line \(x = 1\). This region lies between \(x=0\) and \(x=1\) since \(y=0\) corresponds to the \(x\)-axis and \(y=\arctan(x)\) is above it for \(x > 0\).
Since the solid is formed by revolving the region about the \(y\)-axis, consider using the method of cylindrical shells. The formula for the volume using cylindrical shells when revolving around the \(y\)-axis is: \(V = \int_a^b 2\pi \cdot (\text{radius}) \cdot (\text{height}) \, dx\)
In this problem, the radius of a shell at position \(x\) is the distance from the \(y\)-axis, which is simply \(x\). The height of the shell is the vertical distance between the curves, which is \(\arctan(x) - 0 = \arctan(x)\).
Set up the integral for the volume as: \(V = \int_0^1 2\pi x \cdot \arctan(x) \, dx\)
To find the volume, you would evaluate the integral \(\int_0^1 x \arctan(x) \, dx\) and then multiply the result by \(2\pi\). Integration by parts is a suitable method to solve this integral.

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Volume of Solids of Revolution

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The shell method calculates volume by integrating cylindrical shells formed by revolving vertical slices around a vertical axis. Each shell's volume is approximated by 2π(radius)(height)(thickness). This method is especially useful when revolving around the y-axis and the function is given in terms of x.
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