I can do the first part no problem. I then drew the graph, am I right in saying there is an infinite sequence because the lines intersect an infinite amount of times, because tan is periodic and has vertical asymptotes? I have no idea about showing why the first non rivial zero is bounded like that. I would have thought the trivial zero was at the origin, and the first non trivial was in the range of 0<lambda<pi/2. What am I not understanding here? Thanks edit: oh I think I'm suppose to be looking for solutions in the range of pi and 3pi/2?