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Making Dice, Part 2 (Posted on 2003-04-17) Difficulty: 3 of 5
My friend finished making dodecahedrons, and her next project is to make regular icosahedrons (20-sided dice). Again she wants to know: what is the dihedral angle between any two adjacent faces?

Perhaps this can be solved without the use of spherical trig? ;P

See The Solution Submitted by Bryan    
Rating: 3.7500 (4 votes)

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My last solution is wrong this is the real one | Comment 8 of 10 |
Sorry, I posted a wrong solution, but the real one to this problem is:

Angle=360-ArcSin[1/(√3*Tan[36])]-ArcTan[Sin[63.434948823/2]/(Tan[36]-Sin[63.434948823/2]*√(3*Tan[36]²-1))]
Angle=138.189685105

Where again is used the angle 63.434948823
  Posted by Antonio on 2003-08-21 21:47:11
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