Math Problem Statement
Find the volumes of the solids generated by revolving the triangle with vertices left parenthesis 2 comma 2 right parenthesis, left parenthesis 2 comma 8 right parenthesis, and left parenthesis 6 comma 8 right parenthesis about a. the x-axis, b. the y-axis, c. the line xequals7, and d. the line yequals2. Question content area bottom Part 1 a. The volume of the solid generated by revolving about the x-axis is enter your response here cubic units.
Solution
We are asked to find the volume of the solid generated by revolving a triangle about different axes. The vertices of the triangle are , , and . First, let's handle part a, revolving around the -axis.
Part a: Revolving the Triangle About the -Axis
We can use the method of disks to calculate the volume when revolving around the -axis. The general formula for the volume of revolution using the disk method is:
Here, the height of the triangle above the -axis is given by the vertical distance of the triangle from the -axis (the -values). Since we are rotating the triangle, we must express the edges of the triangle as functions of .
- The vertical line from to is simply a constant line at .
- The line from to is a horizontal line at .
We can break the integral into two parts to capture the geometry of the triangle. First, we need the equation of the slanted line that connects and . The slope of the line is:
Thus, the equation of the line is:
Now, we integrate from to using the disk method with the function .
Volume Calculation
Using the disk method, the formula for the volume becomes:
Substitute the expression for :
Let's calculate this integral.The volume of the solid generated by revolving the triangle around the -axis is cubic units.
Do you want more details on the solution or have any questions? Here are five related questions for further exploration:
- How does the method of cylindrical shells compare to the disk method for revolving around the -axis?
- What is the volume generated if the triangle is revolved around the line instead?
- How does changing the limits of integration affect the volume?
- Can you derive the equation of a curve if the shape was not a straight-edged triangle but a curved region?
- How would the result differ if the triangle had different vertex coordinates?
Tip: When solving volume problems involving rotation, visualize the 3D shape to understand which method (disk, washer, or shell) is best for the given axis of rotation.
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Math Problem Analysis
Mathematical Concepts
Geometry
Calculus
Volume of Solids of Revolution
Formulas
Volume using Disk Method: V = π ∫[a,b] [f(x)]^2 dx
Equation of a line: y - y1 = m(x - x1)
Slope formula: m = (y2 - y1) / (x2 - x1)
Theorems
Method of Disks
Method of Cylindrical Shells
Suitable Grade Level
College Level (Calculus I and II)
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