the vicinity of the point X19, ot op is given approximately by 
multiplying [a5 (# 50) ]° by the cutoff filter given by equation 
(9.68) and integrating the resulting Lebesgue Power Integral 
for the Gaussian case. 
More precisely, the wave system at the source is one system 
from a whole statistical class of systems given by all the poss- 
ible forms the free surface can assume upon forming all of the 
possible limiting partial sums which can be obtained from equation 
(9.48) with all possible combinations of the random phases. Thus 
the disturbance at the source is one of an infinite number of 
possible disturbances for a fixed functional form for [ks (ese Nlan 
and the disturbance in the area of decay is one of an infinite 
number of possible disturbances for a fixed functional form of 
S.F.G.W.F. times [A510 le Also more precisely, when, as in 
the last paragraph, integration of equation (9.71) is referred 
to so glibly, one should think only of some finite partial sum 
evaluated with a sufficiently small net to yield a result ade- 
quate for the problem under study. In addition, the indicated 
forecasted sea surface should be considered to be valid only for 
a relatively short time, and only over a relatively small area 
of the sea surface. 
CS SS 
Three sharp cutoff filters have been described above in 
equations (9.62), (9.63) and (9.68). For a fixed value of x, 
y, and top? they determine an area in the # ,@ plane. Inside 
of this area in the # ,© plane the power spectrum is the same 
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