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: Find the volume

  1. Dec 1, 2012 #1

  2. jcsd
  3. Dec 1, 2012 #2


    Staff: Mentor

    You have a mistake on the next-to-last line. You have evaluated your antiderivative in the wrong order. Inside the parentheses you should have ln(sin(##\pi/2##)) - ln(sin(##\pi/6##)).

    Also, the differential -- dx or du -- should appear in every step until you actually get the antiderivative.

    When you make your substitution, that's when you should either change your limits of integration or at least make a note that the limits are values of x, not u. Here's what I mean:

    $$ \pi \int_{x = \pi/6}^{\pi/2} \frac{du}{u}$$

    By including "x = ..." in one of the limits of integration, that reminds you not to use them directly in the antiderivative that you get.
  4. Dec 1, 2012 #3
    which line I got mistake is last line or what ?
  5. Dec 1, 2012 #4


    Staff: Mentor

    I said which line in my last post.
  6. Dec 2, 2012 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    I pointed out this same omission in your previous thread.
  7. Dec 2, 2012 #6
    Is the final answer is = 2.17 ?
  8. Dec 2, 2012 #7
    Is the final answer will be = 2.17 ?

    anyone help ?
  9. Dec 2, 2012 #8


    Staff: Mentor

    If you round to 2 decimal places, the answer is 2.18.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook