problem in plot of given equation

df=1:300;

nc=1.33;

ns=1.5;

nf=1.59;

theta=10:60

y=zeros(length(theta),length(df))

x=1.5*sind(theta);

l=632.8;

zfc=(l/2*pi)*sqrt(x.^2-nc.^2);

zfs=(l/2*pi)*sqrt(x.^2-ns.^2);

p=1;

de=df+zfc+zfs

y=(nc/x)*((nf^2-x^2)./(nf^2-nc^2))*(zfc/de)*(2*(x/nc)^2-1)^p;

plot(df,y)

iI have problem to plot the graph

[M.MUSBA Elhadid]

The sizes of vectors that are input arguments to plot function have to be the same. So you have to check it.