I need help finishing part of this problem

I really have no idea what goes in the / box part

You can see what I mean in this link, just change the (dot) to a .

http://i40.tinypic.com/30uy3h3.(dot)jpg

(tan^2x)(cot^2x) goes there. Cot =1/tan, so (tan^2x)(cot^2x)=1