Difference between two Sine wave equations
The first equation:

x(t) = Sin(2*pi*F*t)


is for a continuous ("analogue") signal, where t may take any real value.

The second equation:

x(t) = Sin(2*pi*F*n*Ts)


(I assume that this is the correct version - it looks like you have a typo in the question ?)

is for a discrete ("sampled" or "digital") signal, where n is the sample number (integer) and Ts is the sample interval (inverse of sample rate). It has values only at the discrete sampling points where t = n * Ts.

In your MATLAB code you are effectively sampling a continuous function, so although you start off with the first (continuous) equation you end up with the second equation because you are only evaluating (sampling) the continuous function at a set of discrete points.

Note also that as Ts -&gt; 0 the discrete version tends towards the continuous version.