Volume of Triangle Rotated Around Its Base: Shells & Cylinders

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SUMMARY

The discussion focuses on calculating the volume of an object formed by rotating an equilateral triangle around its base using both the shell and cylinder methods. The triangle's angles are established as 60 degrees, leading to a half-angle of 30 degrees for trigonometric calculations. The radius of the circumcircle is determined using the cosine function, where Cos 30 = (side/2)/Radius. The volume formula derived is V = Pi*(R)^2*H, although the axis of rotation remains a point of confusion.

PREREQUISITES
  • Understanding of equilateral triangle properties
  • Knowledge of trigonometric functions, specifically cosine
  • Familiarity with volume calculation methods, including shells and cylinders
  • Basic knowledge of calculus concepts related to rotation
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  • Study the method of cylindrical shells in volume calculations
  • Learn about the application of trigonometry in geometry
  • Explore the derivation of volume formulas for solids of revolution
  • Investigate the implications of the axis of rotation in volume calculations
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Students in geometry and calculus, educators teaching volume calculations, and anyone interested in the mathematical principles of solids of revolution.

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

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