有一次,小明坐着轮船由A点出发沿正东方向AN航行,在A点望湖中小岛M,测得∠MAN=30°,航行100米到达B点时,测得∠MBN=45°,你能算出A点与湖中小岛M的距离吗?
I haven't seen my grandma for a long time. I can't help her very much.
如图四个几何体,其中,它们各自的主视图与俯视图不相同的几何体的个数是( )