Jiajie's nap

虽然不敢确定这不是正确的解法，但好歹是自己想出来，一个很简单的思路，用到了高中学的牛顿运动定律。

问题重述

Pendulum consists of a strong thread and a bob. When the pivot of the pendulum starts moving along a horizontal circumference, the bob starts tracing a circle which can have a smaller radius, under certain conditions. Investigate the motion ......

Example

P=-80:10:0;

U2=[-6.70,-5.98,-5.26,-4.48,-3.69,-2.78,-1.78,-0.80,0.40];

A=polyfit(P,U2,1)

z=polyval(A,P)

plot(P,U2,'.',P,z)