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

  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. CompuChip

    CompuChip 4,297
    Science Advisor
    Homework Helper

    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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