If you use the "soln" structure as result, ode23 only respects start and end point from your tspan vector.
After the integrator has finished, you would have to use "deval" to interpolate the solution to the time points of your choice.
I suggest using the [T,Y] solution structure instead:
% Simulate ODE
c = 0.028;
m = 0.3;
g = 9.81;
y0 = [0; 35*cosd(65); 0; 35*sind(65)];
times = [0:0.1:7];
[T,Y] = ode23(@(t, y) myfun(t, y, c, m, g), times, y0);
xc = Y(:,1);
yc = Y(:,3);
figure
plot(xc, yc)
% define ODE
function dydt = myfun(t, y, c, m, g)
v = sqrt(y(2)^2+y(4)^2);
dydt = [y(2); -c*v*y(2)/m; y(4); -c*v*y(4)/m-g];
end
