Let { ak } be any sequence of real numbers that satisfies
ak ≥ ak+1 > 0 for all k≥1.Let { rk } be the sequence of real numbers that satisfies
rk = ak for k = 1, = ak*√[ 1 - tk*tk ] for k > 1, where tk = ak/(2*rk-1).Clearly, for all k > 1, rk is defined and greater than zero
if tk∈(0,1).
Prove or disprove that tk∈(0,1) for all k > 1.