probability(x=a) = p

probability(x=b) = q

p+q = 1

Expectancy of X = 0

the problem is to compute the limit as N approaches infinity of [f(x/N^.5)]^N

f(x) is the fourier transform

I can only figure out what the fourier transform is, but calculating the limit is what I don't get.

f(x) = p[cos(ta)-i*sin(ta)] + q[cos(tb)-i*sin(tb)]