Volume of Triangle Rotated Around Its Base: Shells & Cylinders

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In summary, the problem involves finding the volume of an object created by rotating an equilateral triangle around its base. This can be solved using both shells and cylinders. To find the radius of the circunference, trigonometry can be used. The volume of the object can then be calculated using the formula V = Pi*(R)^2*H. The axis of rotation is not specified in the problem.
  • #1
youxcrushxme
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I'm having trouble on this problem -

Find the volume of the object created by rotating an equilateral triangle around its base. Solve using both shells and cylinders.

Any help would be appreciated :)
 
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  • #2
Firstly you have to determine the radius of the circunference who contains the triangle. ( see the graphic below)

- triangle is an equilateral triangle, because that the angles are 180/3= 60º

If we draw the radius we have half angle ; 60/ 2 = 30 º

Whe aply trigonometry :

Cos 30 = (side/2)/ Radius --> Here you have only one unknown (radius)

Now, yo have by rotation generated circunference Radius, and the volume of the piece will be :

V = Pi*(R)^2*H

:smile:
 

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  • #3
mmm... where is the axis of rotation that creates the volume?
 

1. What is the formula for calculating the volume of a triangle rotated around its base using the shell method?

The formula for calculating the volume of a triangle rotated around its base using the shell method is V = 2π ∫ab x * h(x) dx, where a and b are the limits of integration and h(x) is the height of the shell at a given value of x.

2. How is the volume of a triangle rotated around its base using the cylinder method different from using the shell method?

The cylinder method involves dividing the triangle into thin vertical slices, calculating the volume of each slice using the formula V = πr2h, and then integrating the volumes of all the slices. This method is often easier to visualize and calculate compared to the shell method, which involves dividing the triangle into thin horizontal shells.

3. Can the volume of a triangle rotated around its base using the shell method be negative?

No, the volume of a triangle rotated around its base using the shell method cannot be negative. This is because the volume of a solid object is always a positive value, and the shell method calculates the volume by adding up the volumes of the individual shells, which are all positive numbers.

4. How does changing the height of the triangle affect the volume when using the shell method?

If the height of the triangle is increased, the volume of the rotated triangle will also increase. This is because the shells used to calculate the volume will have a larger height, resulting in a larger overall volume. Similarly, if the height is decreased, the volume will also decrease.

5. Is it possible to use the shell and cylinder methods to calculate the volume of any solid object?

No, the shell and cylinder methods can only be used to calculate the volume of certain solid objects with specific shapes, such as a triangle rotated around its base. Other methods, such as the disk and washer method, must be used for other shapes like circles and rings. Additionally, the object must have a defined volume in order for these methods to be applicable.

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