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Math Help - Circle Geometry

  1. #1
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    Red face Circle Geometry 3

    Hi



    DA produced and CB produced meet at Q. If angle CDB = angle DQC = x, prove that CD = ca. (Hint: Let angle CBD = y)

    Can anyone please give me a hint on how to do this question?
    Last edited by xwrathbringerx; December 27th 2008 at 02:39 PM.
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  2. #2
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    Quote Originally Posted by xwrathbringerx View Post
    Hi



    DA produced and CB produced meet at Q. If angle CDB = angle DQC = x, prove that CD = ca. (Hint: Let angle CBD = y)

    Can anyone please give me a hint on how to do this question?
    I don't usually do geometry but since my first post was a circle geometry one and since it's the anniversary of my first post I will do this one.

    There's a theorem that tells you that \angle CAD = \angle CBD. Therefore \angle CAD = y.

    From \triangle DBQ it follows that \angle BDQ = 180 - (180 - y) - x = y - x. Then \angle CDQ = x + \angle BDQ = y.

    So \triangle CDA is isosceles etc.
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