Give the smallest number of statistical moment descriptors needed to differentiate between...

Give the smallest number of statistical moment descriptors needed to differentiate between the signatures of the figures shown in Fig.

FIGURE 11.10 Distance-versusangle signatures. In (a) r(θ) is constant. In (b), the signature consists of repetitions of the pattern r(θ) = A sec θ for 0 ≤ θ ≤ π/4 and r(θ) = A csc θ for π/4<θ ≤π/2