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Math Help - formula

  1. #1
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    formula

    r = a*sqrt(b^2-c^2)

    What does b equal to?
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  2. #2
    MHF Contributor Amer's Avatar
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    Quote Originally Posted by the undertaker View Post
    r = a*sqrt(b^2-c^2)

    What does b equal to?
    r=a(\sqrt{b^2-c^2})

    r^2=a^2(b^2-c^2)

    \frac{r^2}{a^2} = b^2 - c^2

    \frac{r^2}{a^2} + c^2 = b^2

    b=\sqrt{ \frac{r^2}{a^2} - c^2}

    that what you mean
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  3. #3
    Super Member flyingsquirrel's Avatar
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    Quote Originally Posted by Amer View Post
    \frac{r^2}{a^2} + c^2 = b^2

    b=\sqrt{ \frac{r^2}{a^2} - c^2}
    No, the last line should read \sqrt{b^2}=\sqrt{ \frac{r^2}{a^2} + c^2} and as \sqrt{b^2}=|b|, there are two solutions : \pm\sqrt{ \frac{r^2}{a^2} + c^2}.
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