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: How does my book get from this step to this step?

  1. Oct 6, 2007 #1
    [SOLVED] How does my book get from this step to this step?

    My book went from int of dx/ ( sqrt(x)*(x+1) )


    2arctan sqrt (x) -- WTH?

    I thought the form for arctan was dx/a^2 + u^2 and I don't see that in the given integrand?

    Can anyone help?
  2. jcsd
  3. Oct 6, 2007 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    Dearly Missed

    Substitute [tex]u=\sqrt{x}[/tex], and see what you get.
  4. Oct 6, 2007 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    If x=u2, then dx = 2 u du

    sqrt (x) = u, and

    x+1 = u2 + 1
  5. Oct 6, 2007 #4
    astronuc, did you arrive at that by using the substitution arildno suggested?
  6. Oct 6, 2007 #5


    User Avatar
    Science Advisor

    Well, arildno said "u= [itex]\sqrt{x}[/itex]" and Astronuc said "x= u2". Look the same to me!
  7. Oct 6, 2007 #6
    Ha, you rascal!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook