这是一个实现单摆功能的程序，区别于以前的只能在一条直线上摆动，而是一个和实际单摆大致相同的，在最高点速度最低，最低点速度最大。-This is a realization of the program pendulum function, distinguished only swing in a straight line before, but an actual pendulum roughly the same, at the highest point of the lowest rate, the lowest point of the maximum speed.