1. The problem statement, all variables and given/known data Determine limA→∞(sinc(x/2A)) 2. Relevant equations I would use L'Hôpital's rule, but I'm not sure if it is valid in this case as the function is that of x, not A. I want to know if it's valid to treat x as constant and take derivatives with respect to A and evaluate as A->inf. 3. The attempt at a solution limA→∞(sinc(x/2A))=limA→∞(sin(x/2A)/(x/2A)) =limA→0(sin((x/2)A)/((x/2)A)) =limA→0(cos((x/2)A)) =1 Is this correct usage of L'Hôpital's rule?