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Math Help - help on angle in circle problem

  1. #1
    Member helloying's Avatar
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    help on angle in circle problem

    help appreciated
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  2. #2
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    Grandad's Avatar
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    Angles in circles

    Hi -

    The sizes of the angles marked in ink are correct. (I assume you know how they were calculated.) All you need to do now is to use: Angle BFC + angle FCG = 180 degrees.

    Grandad
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  3. #3
    Member helloying's Avatar
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    Quote Originally Posted by Grandad View Post
    Hi -

    The sizes of the angles marked in ink are correct. (I assume you know how they were calculated.) All you need to do now is to use: Angle BFC + angle FCG = 180 degrees.

    Grandad
    Ya. i know that. but i dont know how to use. can u kindly teach me?There are two unknown even if i know they add up to 180 degrees.
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  4. #4
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    Angles in circles

    Hi -

    Sorry, you do need a bit more than I said before.

    Join BD to form a cyclic quadrilateral ABDE. Then (as in an earlier question you asked) the angle BDC is an exterior angle to this quadrilateral, and so equals angle EAB, the interior opposite angle.

    So angle BDC = 70 degrees = angle BFC (angles in the same segment).

    Now you can use the fact that angle BFC + angle FCG = 180 degrees to find angle FCE.

    OK now?

    Grandad
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