For different constant values of i and a=0:180,
 how do i plot a 3-D surface  and have like
i1=0 const
i2=45 const
13=90 const
.
.
.
.
i180=180  const
 
a=0:180 for all the values above on the same plot? The code is shown
below.

i = input('Enter the input angle in degrees: ');

a = 1:.5:180;

for j = 1:length(a)

     y(:,j) = ( 1 + cosd(2*a(j))) / (1 + cos(2*(a(j)-i)));

end;

My ultimate goal is to have a single graph with different surfaces in
3-D with variables (a, i, y) on the axes. y=z axis, a=x axis, i=y
axis. Thanks for any help
please help