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If f(x+y) + f(x-y) =2f(x)f(y) and f(0)=k then find f(x)?

  1. May 30, 2008 #1
    if
    f(x+y) + f(x-y) =2f(x)f(y)
    and f(0)=k
    then find f(x)?

    What should be approach followed to solve this question .
    plz ans it soon :blushing:
     
  2. jcsd
  3. May 30, 2008 #2

    CompuChip

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    Science Advisor
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    You have an expression with f(x) and f(y) and you only want f(x). So you have to get rid of y.

    One more hint: that identity holds for all values of y.
     
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