1. The problem statement, all variables and given/known data Given x=n*cos(90-360/n), express n in terms of x 2. Relevant equations <no relevant equation since it's pure maths> 3. The attempt at a solution All I can say is that the result is one of those functions, whose proper name I do not remember, with multiple n values corresponding to one x value. Not sure how to elegantly report that and this is mainly why I asked.