Math Problem Statement
Let [R] be the region enclosed by the line [x=-4], the line [y=1], the line [y=4], and the curve [y=e^x]. Line x = negative 4 and curve y = e to the x power are graphed. The curve moves along the negative x axis, then moves upward with increasing steepness. It intersects the line at (negative 4, 0), then moves upward to the right of it. The area enclosed by the two plots between y = 1 and y = 4 is shaded, representing region R. [y] [x] [\blueD{y=e^x}] [\small -4] [\large R] [\small 1] [\small 4] A solid is generated by rotating [R] about the line [x=-4]. Which one of the definite integrals gives the volume of the solid? Choose 1 answer: Choose 1 answer:
Solution
To find the volume of the solid generated by rotating the region around the line , we need to set up the integral using the method of cylindrical shells.
Step 1: Determine the formula for the volume using cylindrical shells
The formula for the volume using cylindrical shells when rotating around a vertical line (like ) is given by:
Step 2: Identify the radius and height
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Radius: The distance from the axis of rotation to a point on the curve is given by the horizontal distance between and on the curve. Thus, the radius .
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Height: The height of the shell is the difference between the -values, which is (since we are using as the independent variable in this approach).
Step 3: Determine the limits of integration
The region is enclosed between and , so the limits of integration are from to .
Step 4: Set up the integral
Thus, the volume of the solid is:
However, the problem asks which of the definite integrals corresponds to the correct setup. The integral expression that matches the setup described above would be the following:
This represents the correct definite integral to calculate the volume of the solid generated by rotating the region about the line .
Would you like more details on this solution, or do you have any questions?
Relative Questions:
- How would the integral change if the rotation were around instead?
- What is the significance of the height function in the method of cylindrical shells?
- How would you set up the integral if the region was rotated around the y-axis instead of ?
- Can the disk/washer method be applied to this problem? If yes, how?
- What if the curve was replaced with ; how would the integral change?
Tip: Always visualize the region and the axis of rotation to help determine the correct method and setup for the integral.
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Math Problem Analysis
Mathematical Concepts
Calculus
Integral Calculus
Volume of Revolution
Cylindrical Shells Method
Formulas
Volume using cylindrical shells: V = 2\pi \int_{y_{\text{min}}}^{y_{\text{max}}} (\text{radius}) \cdot (\text{height}) \, dy
Theorems
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Suitable Grade Level
Advanced High School
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