1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Why double integral could calculate area and volume

  1. May 4, 2009 #1
    why there are a case where double integral could calculate area
    and in other case
    it could calculate a volume.

    an integral should do only one thing
    not both??

    for what characteristics it could used to calculate area,
    for what its volume
  2. jcsd
  3. May 4, 2009 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi transgalactic! :smile:

    It depends what you're integrating.

    (did you have something specific in mind?)

    For example, with an irregular solid you'd probably need 3 integrals, but with say an irregular cylinder (like a cookie-cutter :wink:), all the heights are the same, so you only use 2 integrals . :smile:
  4. May 4, 2009 #3


    Staff: Mentor

    A definite integral (single, double, are whatever) just represents a number. It's only when we give it context by attaching dimensions (e.g., feet, cm, lb) to the quantities involved does it represent area or volume or work or what-have-you.

    A single integral could represent an area, volume, length, probability, or any number of other concepts, depending on what we have decided to use for units. It's similar for double integrals.

    What makes you think that an integral is supposed to do only one thing?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook