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Arc length of circle

  1. Oct 18, 2015 #1
    • Member warned about posting with no effort shown
    1. The problem statement, all variables and given/known data
    find the arc length of a circle in the first quadrant with an equation x2 + y2 = a2

    2. Relevant equations
    arc length = ∫ √(1 + (dy/dx)2) dx

    3. The attempt at a solution
    i got stuck on how to solve the integral
  2. jcsd
  3. Oct 18, 2015 #2


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    Well, show us where you got stuck.

    Did you calculate dy/dx for the arc of the circle, using its equation?
  4. Oct 18, 2015 #3
    yeah, i make the circle equation into y= √(a2-x2) , and then put it into the arc length equation.
    the problem is i cant solve my integral equation.
  5. Oct 18, 2015 #4


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    You still didn't show the integral you want to solve and how you got it.

    Did you try the usual trigonometric substitutions?
  6. Oct 18, 2015 #5
    first i derive my y=√(a2-x2) into y'= - x/√(a2-x2)
    and then put it into arc length equation = ∫ √(1+(dy/dx)2) dx
    resulting ∫ √(1+(- x/√(a2-x2))2) dx
    and i got stuck there. i dont know how to solve my equation, and i didnt use trigonometric substitution
  7. Oct 18, 2015 #6


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    Then you should try that (after simplifying the expression a bit).
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