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Problem of summation-mathematica

  1. Jan 13, 2012 #1
    MATHEMATICA:differentiate the summation

    I need help.im having problem to differentiate my equation respect to the m_i;How can i differentiate the equation.
    Second question is;When i set Y=2;how can i put the parameter like m_1;m_2;S_1;S_2;
    what i just do is input it manually by changing m_1=m1;m_2=m2;
    its very difficult if Y become larger number
    Code (Text):

    Sum[(Subscript[\[Sigma], i] - Subscript[c, i])*(Subscript[q, i]/
              Subscript[T, i]), {i, 1, Y}] -
       Sum[((1 - \[Beta])/(2 - \[Beta]))*(Subscript[d, i]*
          Subscript[q, i]) +
           (1/2)*((Subscript[m, i] - 1)*Subscript[w, i]*Subscript[q, i]) +
           (Subscript[A, i]/Subscript[m, i] + Subscript[S, i])/
             Subscript[T, i], {i, 1, Y}]
    Thanx for da help

    Attached Files:

    Last edited: Jan 13, 2012
  2. jcsd
  3. Jan 13, 2012 #2
  4. Jan 13, 2012 #3
    Thanx a alot for da help.but what is da function of
    Code (Text):
     d /. Subscript[m, 1] -> 4  
    and do you know how can input the subscript like m_1 and m_2 if they have value ?
  5. Jan 13, 2012 #4
    is an alternate way of writing the ReplaceAll function.
    That function replaces all variable with value in expression.
    Here is the documentation for ReplaceAll.
    If you look at the value of the variable d in my code and compare that
    with the value after the ReplaceAll you can see what it has done.

    I am not certain I understand what you mean "if they have value."
    If they have value then they are not a variable in your expression
    and there is no variable to replace with a value.
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