Another way is to simplify writing, and then consider using Robida's law or equivalent infinitesimal. The purpose of simplification is to find out the product factors with non-zero limits and calculate these limits first. Original limit = lim (1+x) (1-x) * sin (π x/2)/cos (π x/2) = lim (1+x) * sin (π x/2) × lim (/kloc-)