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Thread: More Help With Circles

  1. #1
    Junior Member
    Oct 2008

    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
    Oct 2008
    The arc length is proportional to the angle.
    e.g. $\displaystyle \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 $\displaystyle AD = \pi R $
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  3. #3
    Oct 2008
    I wish i still had this 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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