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  1. #1
    Senior Member Laurel's Avatar
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    Default Geometric Construction Problem

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    Hi

    I've been drawing a cross-section of an aluminium extrusion, and have come up with a problem. If anyone could let me have the solution, I'd be very grateful.

    Starting with a circle and a point. I want to draw a larger circle of given radius, which passes thru the point and touches the smaller circle at a tangent, enclosing it.

    Sounds simple (and it probably is) but it's eluding me at the moment.
    Paul

  2. #2
    Super Moderator SLW210's Avatar
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    I am not really following your explanation. Perhaps you could explain in more detail or put up a sketch.

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    Default

    Are we talking about a reverse or compound curve?
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  4. #4
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    From the centre of the small circle, draw a circle of radius (R large - R small).

    Then from the given "point", draw a circle of radius R large.

    Where these two circles intersect is the proper centre of the large circle which can now be drawn.

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    Banned Alan Cullen's Avatar
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    I think I know what Laurel is after......can't be done in base acad......you need a lisp routine........

    everyone.....take a circle......then take another circle of greater radius that encloses the first circle (tangentially) and passes through a given point.....

    Laurel....acad can't do that (complex cogo)......only a very good knowledge of maths will give you that answer.....or if you beg me enough for my lisp routine........

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    Quote Originally Posted by Alan Cullen View Post
    I think I know what Laurel is after......can't be done in base acad......you need a lisp routine........

    everyone.....take a circle......then take another circle of greater radius that encloses the first circle (tangentially) and passes through a given point.....

    Laurel....acad can't do that (complex cogo)......only a very good knowledge of maths will give you that answer.....or if you beg me enough for my lisp routine........

    Excuse me Alan, but I just did it

  7. #7
    Super Moderator SLW210's Avatar
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    Are you wanting something like this?

    Attachment 1954
    Last edited by SLW210; 7th Feb 2008 at 07:25 pm.

  8. #8
    Senior Member Laurel's Avatar
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    Thank you everyone for your suggestions.

    Eldon (& SLW210) - Your solutions are exactly what I need.

    Told you it would be simple - don't know why it elluded me.

    Thanks again.
    Paul

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