Tracking the frequency of a sinusoid

Curve that is basically sinusoid, but maybe with noise added.

Fundamental Theorem of Trigonometry

sin(n+1)t = 2cos(t)sin(nt) -sin(n-1)t

x = [2*cos(t) , -1]'

A = I (identity, no change)

z _n+1 = observation

H = [z_n, z_n-1]