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Shells & Cylinders

  1. Apr 5, 2007 #1
    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 :)
  2. jcsd
  3. Apr 6, 2007 #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


    Attached Files:

  4. Apr 6, 2007 #3


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