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Jul 29th, 2006

Circles .... Locus...

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My friend just gave me a c++ problem..
well the problem was to make small circles on circumfrence of a big circle that is positioned in the middle of screen...

well i can get that middle of screen by getmaxx()/2 ...
but all i can get to find locus of the circle is throught the formulas :
rcos(theta)
rsin(theta)

but this i suppose wrks only for circle having centre (0,0)..
so im kinda stuck here
any help would be appreciated

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ultra vires

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Jul 29th, 2006

Re: Circles .... Locus...

So just add the centre (cx,cy) to your calculations

C++ Syntax (Toggle Plain Text)
r * cos(theta) + cx;
r * sin(theta) + cy;
r * cos(theta) + cx;
r * sin(theta) + cy;

Salem

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Jul 29th, 2006

Re: Circles .... Locus...

but doesnt rcos(theta) and .... wrks only for that (0,0) circle ??

well let me try it out...will post back .. (currently wrkin with vb

)

btw thnx a lot for replyin....

Last edited by ultra vires; Jul 29th, 2006 at 9:13 am.

ultra vires

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Jul 29th, 2006

Re: Circles .... Locus...

Not to inject extra complexity, but if you need to get those exterior circles to fit together into a nice ring, with each smaller circle touching it's neighbor and the circumference of the big one, then it's math time.
See the Soddy circle page on Mathworld:

http://mathworld.wolfram.com/SoddyCircles.html
Look for Bllew's work (3). Depending on the number of "excircles", it may simply to something easy like the Descartes Circle Theorem.

Last edited by jim mcnamara; Jul 29th, 2006 at 7:52 pm.

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