Can assume limit of f(x) being finite

(11) Let f be a continuous function, positive function defined on [1, co) such that lim f(ar) exists (i.c. the limit is finite) and / f(x)da converges. (a) Does sin( f(er) )dar necessarily converge or necessarily diverge? Prove your answer. (b) Does cos(f(a) )dar necessarily converge or necessarily diverge? Prove your