─ Mrs. Zhang was sent to teach English in a poor mountain village last year.
─ She said she would never forget some pleasant ______ while working there.
如图所示,用一块长L=1.0m的木板在墙和水平地面间架设斜面,斜面与水平地面的倾角θ可在0~60°间调节后固定.将质量m=0.2kg的小物块从斜面顶端静止释放,物块与斜面间的动摩擦因数μ1=0.05,物块与水平地面间的动摩擦因数μ2=0.8,忽略物块在斜面与水平地面交接处的能量损失.(已知重力加速度g=10m/s2;sin37°=0.6,cos37°=0.8最大静摩擦力等于滑动摩擦力)
柑橘的果肉酸甜可口,其酸甜的物质主要储存在细胞的( )里.
双曲线x2a2-y2b2=1a,b>0的左、右焦点分别为F1、F2,过焦点F2且垂直于x轴的直线与双曲线相交于A、B两点,若F1A→·F1B→=0,则双曲线的离心率为____