Minimum number of points to specify a sine wave with a given accuracy
I think what you are asking is "what is the sample rate required to sample a sine wave for a given precision". This is basically what the sampling theorem is all about (See for example http://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampling_theorem). The surprising answer is (more or less): "more than two". Once you meet the sampling criteria you are fine and 
the accuracy does NOT increase by sampling more often.

In your case, 3 points per period will work fine (provided your DAC has a proper anti-aliasing filter).