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: Iterated Integrals

  1. Apr 8, 2005 #1
    i need to solve this
    [tex] \int_{0}^{\sqrt{\pi}} ( \int_{x}^{\sqrt{\pi}} sin y^2 dy) dx [/tex]

    now i know i have to change the order of this
    the integrand is bounded by the triangle from x = 0 to [itex] x= \sqrt{\pi} [/itex] here's where i am stuck
    what is the boundary of the y?? is y bounded below by x=0 and above by x =1??

    so what would the limits of integration change to?? (for the inside one from 0 to root pi?) and the outside one stays the same??

    pelase help!
  2. jcsd
  3. Apr 8, 2005 #2


    User Avatar
    Homework Helper

    Look at the attached figure. You have to integrate for the yellow triangle, according to the boundaries of your original integral. If you change the order of integration, that is you integrate by x first, it would go from x=0 to x=y; and then by y which goes from y=0 to y= sqrt (pi).

    Last edited: Jun 29, 2010
  4. Apr 8, 2005 #3
    how do you know that it is the upper triangle and not the lower triangle??
  5. Apr 8, 2005 #4
    Because in the original integral:

    [tex] \int_{0}^{\sqrt{\pi}} ( \int_{x}^{\sqrt{\pi}} sin y^2 dy) dx [/tex]

    Look at the limits for the dy integral, y goes from y=x to y=root pi. If it were the white triangle in the image, then y would be going from 0 to x.
  6. Apr 8, 2005 #5
    ehild is completely correct

  7. Apr 8, 2005 #6


    User Avatar
    Science Advisor
    Homework Helper

    You may wanna search mathworld for Fresnel' S(x) antiderivative...

    Last edited: Apr 8, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook