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!

Head scratching integral calculus hw

  1. Feb 28, 2005 #1
    hey guys, i need help on my integral calculus hw

    2) int(x*3*e^(x^7)) dx
    this one is just giving me insane problems
     
    Last edited: Feb 28, 2005
  2. jcsd
  3. Feb 28, 2005 #2

    cepheid

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    1) Try the substitution:

    u = (4-t)1/2

    du = -dt / 2(4-t)1/2

    Key thing here: you've got some expression of t and square root of some other expression involving t. Make a substitution to so that u is proportional to square root of t, and therefore t is in terms of u^2, and your integral now has u and u^2 in it. Much easier to work with. No square roots. Just polynomials. That's why I chose that substitution.
     
  4. Mar 1, 2005 #3
    Is this [tex]\int3 x e^x^7{dx}[/tex] or [tex]\int x^3 e^x^7{dx}[/tex]?

    As you have it written, it's a very strange order for multiplication. Either way, it doesn't seem to be a simple, straight-forward answer. The only way I seem to have found so far requires a reduction formula.
     
  5. Mar 1, 2005 #4

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    For the integral
    [tex] \int x \ e^{x^{7}} dx [/tex]

    view the first attachement.

    For the integral
    [tex] \int x^{3} \ e^{x^{7}} dx [/tex]

    view the second...

    Daniel.
     

    Attached Files:

  6. Mar 1, 2005 #5
    If he's still doing normal substitutions, it is doubtful that he is expected to know gamma integral transformations. I think there's a typo in the original poster's post.
     
  7. Mar 1, 2005 #6

    dextercioby

    User Avatar
    Science Advisor
    Homework Helper

    Then let him correct it,else his entire visit to PF has been useless...

    Daniel.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Head scratching integral calculus hw
  1. Calculus hw! (Replies: 20)

  2. Integral calculus (Replies: 3)

Loading...