Chapter 6: Problem 1
The region bounded by \(y=e^{2 x}, y=0, x=-2, x=0\) is rotated around the \(x\) -axis. Find the volume. volume \(=\) ___________.
Short Answer
Expert verified
The volume is \(V = \pi \left[ \frac{1}{4} - \frac{1}{4e^{8}} \right] \)
Step by step solution
01
Identify the General Formula
The volume of a solid of revolution around the x-axis is given by: \[ V = \int_{a}^{b} \pi [f(x)]^2 dx \]where the function is rotated around the x-axis.
02
Determine the Function and Interval
The function given is \(y = e^{2x}\) and the bounds are from \(x = -2\) to \(x = 0\).
03
Set Up the Integral
Substitute the function into the volume formula:\[ V = \pi \int_{-2}^{0} (e^{2x})^2 dx \]which simplifies to\[ V = \pi \int_{-2}^{0} e^{4x} dx \]
04
Integrate the Function
Integrate the function \(e^{4x}\):\[ \int e^{4x} dx = \frac{1}{4} e^{4x} \]Evaluate the integral from \(x = -2\) to \(x = 0\):\[ V = \pi \[ \frac{1}{4} e^{4x} \]_{-2}^{0} \]
05
Calculate the Definite Integral
Evaluate the expression:\[ V = \pi \left[ \frac{1}{4} e^{4(0)} - \frac{1}{4} e^{4(-2)} \right] = \pi \left[ \frac{1}{4} e^{0} - \frac{1}{4} e^{-8} \right] = \pi \left[ \frac{1}{4} - \frac{1}{4} e^{-8} \right] \]
06
Simplify the Result
Simplify the expression to find the volume:\[ V = \pi \left[ \frac{1}{4} - \frac{1}{4e^{8}} \right] \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
volume of solid of revolution
The volume of a solid of revolution is an important concept in calculus. It involves rotating a region or function around an axis to create a 3D shape. To find its volume, we use integration.
For the volume of a solid revolving around the x-axis, the formula used is:
\begin{align*}V = \int_{a}^{b} \pi [f(x)]^2 dx\end{align*}
Where
This setup allows us to slice the solid into thin disks and sum their volumes from \[a \] to \[b \]. Each disk has a volume of \[\pi [f(x)]^2 dx\.\]
For the volume of a solid revolving around the x-axis, the formula used is:
\begin{align*}V = \int_{a}^{b} \pi [f(x)]^2 dx\end{align*}
Where
- \[a \] and \[b \] are the bounds of the region along the x-axis
- \[f(x)\] is the function being rotated
This setup allows us to slice the solid into thin disks and sum their volumes from \[a \] to \[b \]. Each disk has a volume of \[\pi [f(x)]^2 dx\.\]
definite integral
A definite integral computes the accumulation of quantities, often areas under curves. It’s symbolized as:
\begin{align*}\overint{a}{b} f(x) dx\end{align*}
Where
For solids of revolution, integrating from \[a \] to \[b \] with \[dx \] finds the total volume.
In the example, integrating \[e^{4x} \] from \[-2 to 0\] helps calculate the shape’s volume formed by rotating \[y = e^{2x} \].
\begin{align*}\overint{a}{b} f(x) dx\end{align*}
Where
- \[f(x)\] is the function being integrated
- \[a\] and \[b\] represent the start and end points on the x-axis
- \[dx\] indicates integration concerning x
For solids of revolution, integrating from \[a \] to \[b \] with \[dx \] finds the total volume.
In the example, integrating \[e^{4x} \] from \[-2 to 0\] helps calculate the shape’s volume formed by rotating \[y = e^{2x} \].
integration techniques
Effective integration techniques help solve definite integrals.
For the example problem, the integral is set up as:
\begin{align*}\overint{-2}{0} \pi e^{4x} dx\end{align*}
Key steps to solve it:
For the example problem, the integral is set up as:
\begin{align*}\overint{-2}{0} \pi e^{4x} dx\end{align*}
Key steps to solve it:
- Identify appropriate formula: \[V = \pi \overint{a}{b} [f(x)]^2 dx\]
- Transform function: Square the function and simplify, which changes \[e^{2x} \] to \[e^{4x} \]
- Integrate: Use rules of exponential integration, knowing \[\overint e^{kx} dx = \frac{1}{k} e^{kx} \]
- Evaluate at bounds: Substitute in the limits \[-2\] and \[0\] to get the result
exponential functions
Exponential functions, like \[y = e^{2x} \], are a common subject in calculus. They feature a constant base, \[e\] (approximately \[2.718\]), raised to a variable exponent.
Properties of exponential functions include:
In the given problem, the exponential function \[y = e^{2x} \] determines the curve's shape and the solid formed by rotating about the x-axis. Knowing how to integrate such functions is crucial for solving the volume.
Properties of exponential functions include:
- Rapid Growth: They increase or decrease at a faster rate compared to linear or polynomial functions
- Continuous Change: Useful in modeling real-world situations involving growth or decay
- Integration and Differentiation Rules: Their integral and derivatives are straightforward \( \overint e^{kx} dx = \frac{1}{k} e^{kx} \)
In the given problem, the exponential function \[y = e^{2x} \] determines the curve's shape and the solid formed by rotating about the x-axis. Knowing how to integrate such functions is crucial for solving the volume.