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Need help with this circle

  1. Apr 23, 2006 #1
    1. BDC is a minor arc of a circle, centre O. CD is produced to E. If ∠BOC = 110°, find the number of degrees in ∠BDE.

    this is the diagram i came up with,


    by experimentation (i know it's weak), i found ∠BDE to be 55, exactly half of ∠BOC and i can't find a theorem to relate to this. anyone have ideas?

  2. jcsd
  3. Apr 23, 2006 #2


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    If you draw a point P on the major arc of OBC, then there is a theroem which states that: ∠BOC = 2*∠BPC.
    You still need another theroem though, about the opposite angles of a cyclic quadrilateral. Can you find that?
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