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Integrate 4cos(n pi t)

  1. Nov 5, 2009 #1
    1. The problem statement, all variables and given/known data

    integrate:
    4*cos(n pi t) d(t)
    2. Relevant equations



    3. The attempt at a solution

    is it: [4sin(n pi t)]/n.pi

    or

    [4t sin (n pi t)]/n.pi

    any help very much welcome.
     
  2. jcsd
  3. Nov 5, 2009 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    What do you get if you differentiate those?

    [itex]\int cos(u)du= sin(u)+ C[/edit]. What should you let u be? What is du?
     
    Last edited: Nov 6, 2009
  4. Nov 5, 2009 #3
    . What should you let u be? What is du?[/QUOTE]

    Thanks for your quick reply, but you have lost me
     
  5. Nov 5, 2009 #4
    would u = 4

    therefore du=0
     
  6. Nov 5, 2009 #5

    Mark44

    Staff: Mentor

    Nope. Try a different u.
     
  7. Nov 5, 2009 #6
    Look at your given and the general solution:

    [tex]\int 4cos(n\pi t) dt [/tex]

    [tex]\int cos(u)du = sin(u)+ C [/tex]

    Notice the similarity.
     
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