MATLAB: Help in fzero function

fzero

Here x, y,teta are vectors. When I call the function fzero it shows this message:
 fzero(@(t)shkruajek(x,y,1,3,teta,0.1,4,t),0)
Exiting fzero: aborting search for an interval containing a sign change
    because NaN or Inf function value encountered during search.
(Function value at -2.54232e+306 is NaN.)
Check function or try again with a different starting value.
NaN
can you help me to determine where is the problem here??
function [ek]=shkruajek(x,y,i,j,teta,speed,R,t)
ek=sqrt(((x(i)+ speed*cos(teta(i)*t)) - (x(j) + speed*sin(cos(teta(j)*t))))^ 2+ ((y(i) + speed*sin(teta(i)*t)) - (y(j) + speed*sin(teta(j)*t))).^ 2)-R;
end 
a=fzero(@(t)shkruajek(x,y,i,j,teta,speed,R,t),0);

Best Answer

You only provided a single bound, 0, to fzero. It makes guesses about where to look, and it happens to probe at -2.54232e+306 . Something in the calculation there is resulting in NaN being produced.
My guess is that at -2.54232e+306 you have multiple sub-expressions come out as infinite, and that you end up with infinity minus infinity (or negative infinity plus positive infinity). infinity minus infinity is NaN.
You should be considering giving two element bounding vector to fzero instead of just a single location.
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