Dear all, To answer the question as posed,
If w is the line spacing as before and D is the "diameter" of the spiral (i.e. its maximum distance across), you can get the angle needed for the first equation by using the following: A = 0.5 * ( pi + ( 2 * pi * D / w)) Was your question merely out of curiosity (?!) or is there some practical application? David Higgon London
