Hi. The problem seems to be (among others) in your definition of t. Basically, t is empty; perhaps you wanted to write T-ts as upper boundary:
T=2*pi;
ts=0.01;
% t=0:ts:ts-T; % ***
t=0:ts:T-ts;
K=0:60;
N=60;
xt= 2.*sin(4*pi*t) + 5.*cos(8*pi*t);
TK=T'*K;
W=exp(-1i*2*pi/N).^TK;
size(xt) , size(W)
The following lines generated the error, because the sizes of xt and W are different. By the way, you don't need x4 in the rest of the code you posted.
In order to give you a better help, it would be necessary to know with more detail what is the problem you are solving, so that it is possible to have a better understanding of the algorithm you are trying to implement.
% x4=xt.*W;
magx4=abs(xt);
angx4=angle(xt);
figure,subplot(2,1,1);stem(magx4)
figure,subplot(2,1,2);stem(angx4);
Finally, I suggest you to be more specific in the text of your message: "How can I solve this problem" is too generic, and doesn't help. For instance, in this case you could use "Problem with multiplication of variables of different sizes" (this is just my personal point of view).
