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Homework Help: Calculation of complex number

  1. May 1, 2013 #1
    Hi all,
    This is a little problem I'm unable to figure out, in CMPLX mode of my calculator 25i*20i/5i=-100i
    But 25i*20i/(5i) = 100i, Here i=sqrt(-1). What is the difference between these two expressions?
    Thanks for your help.
  2. jcsd
  3. May 1, 2013 #2


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    The difference is that 25i*20i/5i is interpreted as (25i*20i/5)i = (25i*20i/5)*i.
    And 25i*20i/5 = -100.
  4. May 1, 2013 #3
    Thanks a lot for your help, so 'i' is considered as a single complex number.
  5. May 1, 2013 #4


    Staff: Mentor

    Well, yes, but that's not relevant here.

    What Compuchip was talking about was the order of operations. It's the difference between -500/(5i) and (-500/5) * i.

    When you write (or enter) -500/5i, the calculator is interpreting this as -500/5 * i.
  6. May 2, 2013 #5


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    Staff Emeritus
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    In order to avoid ambiguity in expression evaluation, use parentheses in your expressions.
  7. May 2, 2013 #6
    Thanks to all. You all are of great help. I think I can learn a lot from PF.
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