Question

If S = ∑ (log x)^2x/(2n)!, for n ∈ [∞,n = 0]  then S =

(A)   x  + x ^-1 

(B)   x - x^-1

(C)  1/2(x + x^-1)

(D) None of these

Answer 1

Correct option  (C)  1/2 (x + x^-1)