Solve an eqution in matlab

Hello! How can I write this equation in matlab: The variable here is t, all other variables including Rt are known.I want to find t by solving D(t)=R(t).

Answer 1

[Niels]

D(t)=R_t
<=> D(t)-R_t=0

use fzero

tSolution=fzero(D(t)-R_t,0)

but care, the output can be contain more than 1 solution, if D and R have more than 1 intersection point

[ana take]

 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.

ans =

   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);

[Niels]

this means that the function has no roots... maybe plot the function first or check if it has a sign change. Did you enter the right function?