I didn't think this would be hard. —Dan ----- A very nice identity for analytic functions is given by (*) π cot(π z) = lim Sum_{-N <= n <= N} 1/(z-n) N—>oo or briefly: oo = "Sum 1/(z-n)" -oo The series (*) is convergent for each z in C - Z (the non-integral complex numbers) (e.g., see https://people.reed.edu/~jerry/311/cotan.pdf). Puzzle: ------- Determine which function is given by the corresponding infinite product where it converges: f(z) = lim Product_{-N <= n <= N} (1 + 1/(z-n)) N—>oo -----