.在极坐标系中，已知圆ρ＝2cosθ与双曲线ρ2cos2θ－4ρ2sin2θ＝4.则它们的交点的直角坐标为 .
(2,0)
如图甲所示，质量不计的弹簧竖直固定在水平面上，t=0时刻，将一金属小球从轻弹簧正上方某一高度处由静止释放，小球落到弹簧上压缩弹簧到最低点，然后又被弹起离开弹簧，上升到一定高度后再下落，如此反复。通过安装在弹簧下端的压力传感器，测出这一过程弹簧弹力F随时间t变化的图象如图乙所示，则
A．小球加速度的最大值等于重力加速度g
B．小球所受弹力的最大值等于其重力大小的2倍
C．t2~t3这段时间内，小球增加的动能等于弹簧减少的弹性势能
D．t2时刻，小球与弹簧组成的系统的势能出现最大值
用所给单词的适当形式填空.
1. My father likes reading and _____ (listen) to Beijing Opera.
2. —_____ your teacher _____ (wear) glasses?
—Yes, she does.
3. Bill with his father _____ (play) the guitar at the school now.
4. The _____ (high) of the building is about 100 meters．
5. My friend, Tina, _____ (look) like my sister very much.
2,0) 
2,0) 