v=5; t=3; L=5; g=9.81;
tolerance = 1e-5;
rel_error = 1;

%initial guesses
xl = 0.01;
xu = 10;
xr = (xl + xu)/2;

while (rel_error > tolerance)
fxr = v/sqrt(2*g*xr) - tanh (t/(2*L)*sqrt(2*g*xr));
fxl = v/sqrt(2*g*xl) - tanh (t/(2*L)*sqrt(2*g*xl));
if (fxl*fxr<0)
	xu = xr;
else
	xl = xr;
end
xrold = xr
xr = (xl + xu)/2;
rel_error =abs((xr - xrold)/xr)*100;
end
root = xr