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Thread: Find X

  1. #1
    Platinum Lounger
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    Find X

    I'm stuck with this one... or maybe I'm missing the obvious. The (PI)rt measurement is the arc length of the larger circle.
    Angle X=?

    Alan
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    Plutonium Lounger
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    Re: Find X

    You can draw a line between the endpoints of the arc.
    The angle at the centre of the circle is pi * rt / (r+t).
    Use the cosine rule to compute the length of the line you've just drawn, and also of the "left leg" of the angle x.
    Now you know the three sides of the upper triangle, and you can use the cosine rule to compute the cosine of x.

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    Re: Find X

    Thanks Hans. I had actually thought of using that exact method (truly!) but then saw it as too complex, convinced that I'd forgotten one of those handy rules about inscribed/ circumscribed circles and such. I'll now proceed with the symbol crunching.

    Alan

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