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Math Help - More Help With Circles

  1. #1
    Junior Member
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    More Help With Circles

    3. Pic 3. Find mBC

    A. 7 degrees
    B. 166 degrees
    C. 97 degrees
    D. 83 degrees

    7. Pic 7. Find mAE

    A. 110 degrees
    B. 150 degrees
    C. 210 degrees
    D. 127 degrees

    9. Pic 9. Find mBCE

    A. 110 degrees
    B. 70 degrees
    C. 210 degrees
    D. 55 degrees

    16. Pic 16. Find mBD

    A. 180 degrees
    B. 55 degrees
    C. 115 degrees
    D. 127 degrees

    I am between 2 answers on each of these. i don't know which one. can you tell me.
    Attached Thumbnails Attached Thumbnails More Help With Circles-pic-3.jpeg   More Help With Circles-pic-7.jpeg   More Help With Circles-pic-9.jpeg   More Help With Circles-pic-16.jpeg  
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  2. #2
    Senior Member vincisonfire's Avatar
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    The arc length is proportional to the angle.
    e.g.  \frac{AD}{180}=\frac{BC}{83} (AD and BC are arcs)
    You can only express those with respect to the diameter.
    You should have seen that AD = \pi R
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  3. #3
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    I wish i still had this stuff...lol...its easy, if line AD is a Diameter then half the circle is 180*, knowing this if you know <AB is 40 and <CD is 57 then you add those together and subtract from 180 which <BC= 83*

    Also if you know <DE is 70* then you subtract that from 180 and that <AE= 110*


    And so on.....hope this helped^^
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