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Diff equation last step of the solution

  1. Jul 11, 2009 #1
    after solving a long diff question i got

    0.5*u(t+1)-0.5*u(t-1)

    where u(t) is a step function for t>=0 its 1
    and t<0 its 0

    my expression looks pretty finite to me

    how to continue??
     
  2. jcsd
  3. Jul 11, 2009 #2

    Hootenanny

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    I don't understand the question. Does your expression form part of an equation? What is the end goal?
     
  4. Jul 11, 2009 #3
    my expression is the final solution
    but i was told that it cam be developed further more

    how??
     
  5. Jul 11, 2009 #4

    Hootenanny

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    You're expression cannot be the final solution since it is not an equation! What is on the left hand side of the equality sign?

    However, linear combinations of heaviside (step) functions can often be written in terms of the rectangular function.
     
  6. Jul 11, 2009 #5
    believe me there is a left side
    its some intergral
    and its not important

    how to write it in terms of the rectangular function?
     
  7. Jul 11, 2009 #6

    Hootenanny

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    Okay, if you say so.
    Try googling rectangle function.
     
  8. Jul 11, 2009 #7
  9. Jul 11, 2009 #8

    Hootenanny

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    Well you obviously didn't look hard enough since the answer is virtually given in the second equation!
    I'm here to help you with your work, but I'm not simply going to give you the answer.
     
  10. Jul 11, 2009 #9
    ok so look at it as if
    i asked to solve the whole question
    and i showed the solution till some point
    and i need to finish it

    by saying
    "I'm here to help you with your work, but I'm not simply going to give you the answer."

    you are not helping at all
    you could give a hint
    or a article

    but you didnt
     
  11. Jul 11, 2009 #10

    Hootenanny

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    I did give you a hint in post #6, which lead you to an article. I then gave you another hint in post #8, the answer is given there in the second formula on the wiki page!
     
  12. Jul 11, 2009 #11
    the formula is with (t-0.5)

    and i have t-1

    how to suit it with my expression
     
  13. Jul 11, 2009 #12

    Hootenanny

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    Let's have a look at the expression,

    12bbbf9bd48745e67223553a4c97510d.png

    And compare with your expression,

    [tex]f\left(t\right) = \frac{1}{2}\left[u\left(t+1\right)-u\left(t-1\right)\right][/tex]

    So, what do you have to set tau to, in order to make wiki's expression the same as yours?
     
    Last edited: Jul 11, 2009
  14. Jul 11, 2009 #13
    so tao=2

    so its f(t)= [rect(t/2)]/2

    correct?
     
  15. Jul 11, 2009 #14

    Hootenanny

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    Indeed it is :approve:
     
  16. Jul 11, 2009 #15
    thanks
     
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