As others are pointing out: the paper's title is "elementary" (not "trivial" a in the current link title). Both of these have different and accepted meanings i

As others are pointing out: the paper's title is "elementary" (not "trivial" a in the current link title). Both of these have different and accepted meanings in mathematics. "Elementary" roughly means doesn't bring in results from different fields (such as using calculus to prove a theorem about a sum or product). "Elementary" proofs can be quite difficult, and it can be quite a feat (well worth a publication) to find one for a standard result. "Trivial" usually means something closer to easy, or means there is some linkage already implying the result (just in disguise).