You are not logged in.
#1 2013-01-13 16:26:12
- rajinikanth0602
- Member
Offline
another challenging problem for all
can any one say the angle between the planes in a pentagon ball???????
#2 2013-01-13 18:15:17
- bob bundy
- Moderator
Offline
Re: another challenging problem for all
hi rajinikanth0602
Yes, I expect someone can. But shouldn't you respond to
http://www.mathisfunforum.com/viewtopic.php?id=18761
first?
Bob
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei
#3 2013-01-14 17:44:20
- Agnishom
- Super Member
Offline
Re: another challenging problem for all
According to wikipedia, and what I understood, such a solid is a dodecahedron.
And the requied angle is 116.57°.
I shall be waiting eagerly for someone to explain why
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'The whole person changes, why can't a habit?' -65
#4 2013-01-14 19:53:35
- bob bundy
- Moderator
Offline
Re: another challenging problem for all
hi Agnishom,
I've done a few of these over the last two years. The method uses vector geometry and the cosine rule. See
http://www.mathisfunforum.com/viewtopic.php?id=16061
Post 30.
I think Wiki also gives the co-ordinates of the points in 3D so you can pick two adjacent faces, get the critical lines and apply the method.
I've got a post to make for MIF, so It'll be a while before I can put all the figures to this, so have a go yourself. 
Bob
ps. I have a vague memory that I have done it in a thread, but I couldn't find it.
You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei