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Math Help - Arc Length!!

  1. #1
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    Arc Length!!

    Show that the circumference of the unit circle is 2 *integral from -1 to 1 of 1/sqrt(1-x^2)

    hint: use the equation x^2+y^2=1 and the arc length formula

    I simplified my answer down to the integral from -1 to 1 of 1/sqrt(1-x^2) but how do i get it to be two times the whole thing?
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Arc Length!!

    You need to double it since you are only using one half (probably the top or positive root).
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  3. #3
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    Re: Arc Length!!

    this is my work for the problem, where am i using only one half of the square root? i dont really get that. but i would need to write that in my work instead of just magically getting a 2 there at the end! thank you for your help!Arc Length!!-photo.jpg
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Arc Length!!

    You third step, where you take the positive root of y...this represents only the top half of the circle.
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  5. #5
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    Re: Arc Length!!

    Thank you!!
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