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Math Help - C=2 pi r (how do i make 'r' the subject?)

  1. #1
    Junior Member turbod15b's Avatar
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    C=2 pi r (how do i make 'r' the subject?)

    c=2 pi r

    get rid of r?
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by turbod15b View Post
    c=2 pi r

    get rid of r?
    c=2\, \pi\, r

    divide both sides by 2\, \pi

    to get:

    \frac{c}{2\,\pi}=r,

    or:

    r=\frac{c}{2\,\pi}


    RonL
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  3. #3
    Junior Member turbod15b's Avatar
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    ty

    if pi=3.142 and c=2.84cm

    how do i find 'r' ? to 2 significant numbers?

    3.142*2.84=8.9?
    Last edited by turbod15b; December 5th 2006 at 09:23 AM.
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by CaptainBlack View Post
    c=2\, \pi\, r

    divide both sides by 2\, \pi

    to get:

    \frac{c}{2\,\pi}=r,

    or:

    r=\frac{c}{2\,\pi}


    RonL
    Quote Originally Posted by turbod15b View Post
    ty

    if pi=3.142 and c=2.84cm

    how do i find 'r' ? to 2 significant numbers?

    3.142*2.84=8.9?
    Please see CaptainBlack's post.
    r = \frac{c}{2 \pi} = \frac{2.84 \, cm}{2 \cdot 3.142} = 0.45191 \, cm = 0.45 \, cm

    -Dan
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  5. #5
    Junior Member turbod15b's Avatar
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    aint it 28.4/(2x3.142)=4.5 > 2 significant numbers

    radius = circumference/(2*pi)
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  6. #6
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by turbod15b View Post
    aint it 28.4/(2x3.142)=4.5 > 2 significant numbers

    radius = circumference/(2*pi)
    (shrugs) You posted "2.84" in your last post. Either way, the problem is done the same way.

    I'm not sure, did you have a question about 4.5 having 2 significant figures?

    -Dan
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  7. #7
    Junior Member turbod15b's Avatar
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    yeh i meant 28.4cm sorry
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