At 11:31 AM +1200 5/1/07, Robert Allely wrote: > >Hullo - does anyone know if reverse cosine can be calculated in ingres/ OpenROAD? Ie. Cos (:radians) is known, find :radians? > I think there's an arctan function, and you can get arccos from it with the formula arccos(x) = arctan(sqrt( (1-x^2)/x)) Karl