Using ‘fzero’ on that particular problem is needlessly inefficient. You can use ‘atan2’ and ‘asin’ instead.
cn = cos(t1)+cos(t2)+...+cos(tn);
sn = sin(t1)+sin(t2)+...+sin(tn);
p = atan2(sn,cn);
as = asin(y/sqrt(sn^2+cn^2));
T1 = p-as; % One solution (in radians)
T2 = p+as-pi; % Another solution (in radians)
Also any multiple of 2*pi added or subtracted from T1 or T2 is a solution. (Note that the inequality y^2<=sn^2+cn^2 must be true for a solution to exist.)
