The Depression was still going on, but I was in good spirits. I was going to graduate from elementary school, yet my mother 36 dressed me in shorts. Most of my classmates had given up 3
Like all big cities, Paris has a traffic problem: lots of cars, lots of traffic jams(阻塞) and lots of pollution from exhaust fumes(废气). So the city began a scheme(计划) to improve the
的坐标为
，试在空间直角坐标系中作出点
可知点
在
轴上的射影为
，在
轴上射影为
，以
为邻边的矩形
的顶点
是点
坐标平面上的射影，
．
个单位，