Max Volume of Cylinder Inscribed in Cone: 10r^3π

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Homework Help Overview

The problem involves finding the maximum volume of a right circular cylinder inscribed in a cone with a height of 10 and a base radius of 3. The volume of the cylinder is expressed in terms of its radius and height.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the use of similar triangles to relate the dimensions of the cone and the inscribed cylinder. There are questions about whether the focus is on volume or surface area, and the level of calculus required for the solution. Some participants suggest using calculus of variations, while others clarify that the problem is rooted in maximizing the volume of the cylinder.

Discussion Status

There is an ongoing exploration of the relationships between the dimensions of the cone and cylinder. Some participants have provided insights into the use of similar triangles and differentiation to approach the problem. However, there is no explicit consensus on the best method to proceed.

Contextual Notes

Participants note the need to clarify the problem's requirements, including the specific focus on maximizing the volume of the cylinder rather than other potential interpretations. There is also mention of the level of calculus involved, indicating a range of approaches being considered.

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Homework Statement


A right circular cylinder in inscribed in a cone with height 10 and base radius 3. Find the largest possible voluem of such a cylinder.

Homework Equations


[tex]V=\pi*r^2*h[/tex]



The Attempt at a Solution


Ok, so I used similar triangles of the cone and cylinder to obtain h=(10/3)r
I substituted that in for h and I'm not sure where to go from there.
 
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Volume or surface area? What level of calculus is this? Were you trying to give the volume of a cone or of the cylinder? I would solve the problem with calculus of variations by minimizing the integral of the surface area, but that is something that requires differential equations.
 
Calc 1, we are trying to maximize the volume of a cyclinder inside a cone with the given information.
 
Weave said:

Homework Statement


A right circular cylinder in inscribed in a cone with height 10 and base radius 3. Find the largest possible voluem of such a cylinder.

Homework Equations


[tex]V=\pi*r^2*h[/tex]



The Attempt at a Solution


Ok, so I used similar triangles of the cone and cylinder to obtain h=(10/3)r
I substituted that in for h and I'm not sure where to go from there.
Look more closely at your similar triangles. You have a large triangle (the entire cone) and a small triangle (the area inside the cone above the cylinder). If the cylinder has height h and radius r, then similar triangles gives (10-h)/r= 10/3 or 10-h= (10/3)r so h= 10- (10/3)r= 10(1- r/3). Putting that into [itex]V= \pi r^2 h[/itex] gives [itex]V= 10\pi (r^2- r^3/3)[/itex]. Differentiate that with respect to r and set the derivative equal to 0.
 
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