如图所示,一束光线垂直射到玻璃砖的一个面.作出这束光线进入玻璃砖内的径迹和从斜面离开玻璃砖后的大致径迹.要求在斜面处标出法线.
On the way, we s____(发现,注意到)a man holding a piece of paper that said, “Lost my job, family to feed.”
已知数列{an}的前n项和为Sn,a1=2,Sn=n2+n.
(1)求数列{an}的通项公式;
(2)设{1Sn}的前n项和为Tn,求证Tn<1.