Math Is Fun Forum

niharika_kumar

Member

From: Numeraland

Registered: 2013-02-12

Posts: 1,062

2 questions

1.what is a rectangular parallelopipe?

2. what is the ratios of areas of incircle and circumcircle of an isosceles right angled triangle?

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friendship is tan 90°.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,643

Re: 2 questions

hi Niharika

(i)  Sounds like just another name for a cuboid:

http://en.wikipedia.org/wiki/Parallelepiped

Look at the special cases section.

(ii)  Working on it. 

LATER EDIT: (diagram in next post)

In my diagram the radius of the circumcircle is AF.  If you let AC = CB = a then you can get an expression for the area in terms of a.

G is the centre of the incircle so its radius is BFtan(22.5)  So you can get an expression for its area in terms of a.

As both will have a^2 this will cancel when you divide one by the other.

I've done that by measurement on my diagram and it doesn't appear to be any simple value.

Bob

Last edited by Bob (2014-01-31 20:45:19)

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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
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,643

Re: 2 questions

diagram here

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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
Sometimes I deliberately make mistakes, just to test you!  …………….Bob