Scientists have recently discovered that mothers tend to hold their baby on the left．Of 255 right-handed mothers，83％ held the baby on the left．And out of 32 left-handed women，78％held the b
Have you ever seen snow? Many people in the world have not. Some countries never have snow; some have only a little on the tops of very high mountains. In the north of England, there is quite a lot of
绕焦点
按顺时针方向旋转
，设此时抛物线上的最高点为
，则
.
