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Triacontahedron [message #57431] Sun, 25 November 2012 16:38 UTC Go to next message
avatar Magic is currently offline Magic
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The Rhombic Triacontahedron is one of my favorite polyhedron.
You can include a dodecahedron and an icosahedron inside it.
I made a model showing those two polyhedra included into a Triacontahedron.
http://images1.sw-cdn.net/model/picture/674x501_745318_667671_1353770592.jpg
The Triacontahedron is in yellow, the dodecahedron in red and the icosahedron in blue.

The goal of this model is to show how to calculate the volume of the Triacontahedron using those two inclusions. You also need to know that the diagonal (that is the distance bewteen two non consecutive vertices) of a pentagon is the size of its side multiplied by φ, and you need to know how to calculate the volume of a pyramid (one third of the area of its base multiplied by its height).
This video can help.

So can you calculate its volume?
Wink

So many things to design, so little time...
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Re: Triacontahedron [message #57912 is a reply to message #57431 ] Mon, 03 December 2012 14:13 UTC Go to previous messageGo to next message
avatar bartv is currently offline bartv
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Community Manager Europe | Shapeways
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Re: Triacontahedron [message #57918 is a reply to message #57912 ] Mon, 03 December 2012 19:00 UTC Go to previous messageGo to next message
avatar Magic is currently offline Magic
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Registered: August 2008
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Laughing
OK, perhaps some hints are needed...

Hint #1:
The volume of the triacontahedron is 30 times the volume of a pyramid whose base is one of the 30 rhombi and whose apex is the center of the triacontahedron.

So many things to design, so little time...
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Re: Triacontahedron [message #57973 is a reply to message #57918 ] Tue, 04 December 2012 20:11 UTC Go to previous messageGo to next message
avatar Magic is currently offline Magic
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Registered: August 2008
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Hint #2:
The volume of a pyramid is one third of the area of its base multiplied by its height.

So many things to design, so little time...
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Re: Triacontahedron [message #58064 is a reply to message #57973 ] Wed, 05 December 2012 22:07 UTC Go to previous message
avatar Magic is currently offline Magic
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Registered: August 2008
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Hint #3:
AB and A"B" are parallel and have the same size.
index.php?t=getfile&id=23953&private=0
This is due to the facts that
- ABB'A' is a parallelogram (actually a rhombus) thus AB and A'B' are parallel and have the same size.
- A'B'B"A" is a also parallelogram (actually a rhombus too) thus A'B' and A"B" are parallel and have the same size.
- By transitivity, AB and A"B" are also parallel and have the same size.


  • Attachment: tria010.jpg
    (Size: 33.10KB, Downloaded 64 time(s))

So many things to design, so little time...
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