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#1 2010-06-20 01:49:58

lakeheadca
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Find diameter

how to find the diameter of the given figure.
thank you so much guys, specially bobby who always help so fast. He is great.


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#2 2010-06-20 03:45:06

bobbym
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Re: Find diameter

specially bobby who always help so fast. He is great.

Yea, he is, when I grow up I want to be him.

We need to find r of the small circle. Fortunately there is a relationship that does all the work. There is an easier one that relates r to the heights but I am too lazy to look for it.



Where B1 is the area of the smaller circle. B2 is the area of the larger circle. h1 = height from the apex to smaller circle and h2 to the larger.



Do you see that it contains the little r we need. Like magic.

Cross multiply:



Divide both sides by pi.



Divide both sides by 144:



r = 6 and r = -6

Can't have a radius of - 6 so r = 6 and d = 2r = 12.

diameter of smaller circle is 12


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.
 

#3 2010-06-21 03:05:14

lakeheadca
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Re: Find diameter

Amazing !!!
(Thanks * 1000)

 

#4 2010-06-21 03:12:30

bobbym
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Re: Find diameter

Hi lakeheadca;

Glad to help. Bring more!


In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.
 

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