設 a_1,a_2,\cdots,a_n,\cdots 是一公比為 \frac{1}{2} 的無窮等比數列且 a_1=1。試問以下哪些數列會收斂？
a_1,a_2,\cdots,a_n,\cdots
\frac{1}{2}
a_1=1
-a_1,-a_2,\cdots,-a_n,\cdots
{a_1}^2,{a_2}^2,\cdots,{a_n}^2,\cdots
\sqrt{a_1},\sqrt{a_2},\cdots,\sqrt{a_n},\cdots
\frac{1}{a_1},\frac{1}{a_2},\cdots,\frac{1}{a_n},\cdots
\log a_1,\log a_2,\cdots,\log a_n,\cdots
