Minimum number of points to specify a sine wave with a given accuracy I am generating a sine wave from a DAC at a constant frequency. If each full cycle is specified by N data points what is the relationship between the accuracy of the rendered sine wave and N?

N=1 will obviously be pulses. N=4 (peaks and zero crossings) will yield a triangular wave of sorts. Is there some equation that shows how good a sine wave approximation is being created? [Obviously I can put it through a post DAC filter to smooth it etc]

The kind of answer I am looking for is: "Specifying a sine wave with N points yields 1:X 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).