problem 31, but use complex numbers not phasors.
Note generally we've use Re (real part) to generate cos;
here you'll want to use Im (imaginary part) to generate sin.
See the online solution to 16-37 in solutions/16.pdf if
you are unsure how to proceed.
Consider the setup of problem 32: double slit, D=4m, lambda=580nm,
d=4.5µm. Using your favorite computer plotting program, produce
a hardcopy plot of the intensity vs. y for y ranging from -1m to +1m.
Make another such hardcopy plot where there are 4 rather than 2 slits
all separated by d. Finally make a third hardcopy plot where there
are 16 slits separated by d. (I.e., do plots for N=4 and N=16 in
addition to N=2.) The numerical value of the light intensity
is undetermined in the problem so take I0=1
Note that in my favorite plotting program I'd type:
Plot[4 Cos[ Pi (4.5/.580) (y/Sqrt[4^2+y^2]) ]^2,{y,-1,1}]
to do the N=2 case. (The result should look a bit like Fig 35-12.)