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Math Help - Measure of angle D

  1. #1
    rcs
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    Measure of angle D

    ABCD is inscribed in circle O. If angle B is 110 and angle C is 80. What is angle D?

    whatt made me confuse here is that we know that consecutive angles of a quadrilateral are supplementary but 110 + 80 is 190. It impossible now to find angle D. Please guide me on this


    thanks
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Measure of angle D

    What we know is that opposite angles of a cyclic quadrilateral are supplementary.
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    Re: Measure of angle D

    There is no such property as mentioned: consecutive angles of a quadrilateral are supplementary.
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    Re: Measure of angle D

    Quote Originally Posted by ibdutt View Post
    There is no such property as mentioned: consecutive angles of a quadrilateral are supplementary.
    @ibdutt, I hope that you just over looked the term cyclic.
    It is certainly true that opposite angles of a cyclic quadrilateral are supplementary.

    What is not true is "consecutive angles of a quadrilateral are supplementary." That is the true of a parallelogram.
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    Re: Measure of angle D

    Thanks for your response. I stick to my response that "consecutive angles of a quadrilateral are supplementary" there can be no doubt that the opposite angles of a cyclic quadrilateral are supplementary..
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  6. #6
    rcs
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    Re: Measure of angle D

    i know now the answer and i got it... it is 70 degrees
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