1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Differentiation of Geomertic Objects

  1. Apr 8, 2008 #1
    [URGENT] Differentiation of Geomertic Objects

    1. The problem statement, all variables and given/known data

    A sector of a circle has area 100cm². Show that the perimeter of this sector is given by te formula P = 2r + 200/r

    2. Relevant equations

    Area of sector = (angle/360) x pi x r^2
    Permiter of sector = (angle/360) x 2 pi x r

    3. The attempt at a solution

    I've tried but i don't really have time to write it all out. Can someone just show me how to do this one, so that i can try the other questions in the chapter

    Thanks
     
  2. jcsd
  3. Apr 8, 2008 #2
    There's no differentiation involved that I see. Your "perimeter equation" is actually the equation of the arc length of a circle of radius r through angle theta. The actual equation would be the sum of the arclength as well as the two segments which go from the radius inward toward the center of the circle.

    Your area equation has 2 different parameters, r and theta. Given an r, you can find theta, so solve for theta in that equation and plug it into your equation for the perimeter. Use theta in radians.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?