Изменения

С другой стороны,

1 + \frac13 {\left ( \frac1{2n + 1} \right )}^2 + \frac15 {\left ( \frac1{2n + 1} \right )}^4 + \dots < 1 + \frac13 {\left ( \frac1{2n + 1} \right )}^2 + \frac13 {\left ( \frac1{2n + 1} \right )}^4 + \dots = \\

= 1 + \frac13 q_n^2 + \frac13 q_n^4 + \dots = 1 + \frac13 \left ( \frac{q_n^2}{1 - q_n^2} \right ) = \\