Results 1 to 5 of 5

Math Help - Due tomorrow, calculus question invlolving circumference and diameter

  1. #1
    Newbie
    Joined
    May 2008
    Posts
    4

    Due tomorrow, calculus question invlolving circumference and diameter

    The diameter of a tree was 25 cm. During the following year the
    circumference increased by 5 cm.
    Using calculus, find

    (a)
    how much the tree’s diameter has changed ?

    (b) what is the corresponding change in the tree’s cross-section area ?

    I just dont know what to do.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Newbie
    Joined
    May 2008
    Posts
    5
    The two equations you need are:
    2*pi*radius = circumference
    pi *(radius)^2

    radius is half the diameter
    so before the increase in circumference occured, the circumference was

    2*pi*25 cm = 50 * pi cm

    increasing this by 5 cm gives us

    new circumference = 50*pi + 5

    using this to find the radius

    50*pi + 5 = 2*pi*radius
    solving for the radius by dividing both sides of teh equation by 2*pi gives

    new radius = (50*pi + 5)/(2*pi)

    doubling to give diamter

    new diamter = (50*pi +5)/pi

    change in diameter = new diamter - old diamter

    = (50*pi +5)/pi - 25 cm

    new cross section area = (new radius ^2) * pi
    old cross section area = (old radius ^2) * pi
    difference in cross section area = new cross section - old cross section


    That should get you through it, year 7 maths can be tough!!!University gets much worse!!!
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    May 2008
    Posts
    4
    is that calculus? because usually it seems to involve dy/dx and stuff like that.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    May 2008
    Posts
    5
    It is still calculus, algebra is calculas lol, ask your teacher or a friend, but I'm pretty certain thats right, there shouldnt be an differentiating
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    May 2008
    Posts
    1
    I'm guessing your from Griffith [question is identical to the one we were given and it's due at the same time] , if you are, it gives you a hint at the bottom of the assignment, which is to use the small change formula... Examples of the small change formula are on page 136 of the module 2 lecture note book.


    if this helps at all.... you'll want to find a formula that relates to the diameter and circumference, re-arrange if necessary to relate it to what you want to find, which is the diameter, find the derivative of the equation, times the derivative by the change.
    Last edited by Trozza; May 29th 2008 at 06:02 AM. Reason: fix up explination
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Graphs, Diameter related question.
    Posted in the Discrete Math Forum
    Replies: 6
    Last Post: January 11th 2011, 01:05 PM
  2. Diameter question.
    Posted in the Geometry Forum
    Replies: 4
    Last Post: June 2nd 2010, 09:35 AM
  3. Diameter, circumference, area
    Posted in the Geometry Forum
    Replies: 1
    Last Post: May 12th 2009, 07:35 AM
  4. Replies: 4
    Last Post: December 9th 2008, 09:29 PM
  5. Replies: 2
    Last Post: May 28th 2008, 09:36 AM

Search Tags


/mathhelpforum @mathhelpforum