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#1 2016-03-23 15:41:32

Monox D. I-Fly
Member
Registered: 2015-12-02
Posts: 857

[ASK] Volume of Icosahedron

FsdOE.png
I want to prove the formula of regular icosahedron's volume. The reference says that the volume is

. For this, I need to split the icosahedron to 20 triangular pyramid with the same size. I assumed that the base area is
and the pyramid's height is
(I assumed that the pyramid's height should be equal the distance from midpoints of A'B' to the center point of pentagon A'B'C'D'E'. However, no matter how hard I tried and changed the form, I was unable to reach the form
. Is the pyramid's height not equal the distance from midpoints of A'B' to the center point of pentagon A'B'C'D'E'? If so, how to determine their distance?

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#2 2016-04-01 04:36:02

bob bundy
Administrator
Registered: 2010-06-20
Posts: 8,138

Re: [ASK] Volume of Icosahedron

see Maths Teaching Resources.

Bob


Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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