以下代码对我有用，但是我不确定100％是否正是您想要实现的.如果不是，请相应地更新您的问题.

The following code worked for me, however I am not 100% sure if this is exactly what you want to achieve. If it is not, please update your question accordingly.

syms a;
th = sym('th(t)');
x = a*cos(th);
v = diff(x);
acc = diff(v);
accByTh = diff(acc,t);
ezplot(subs(accByTh,th,'a*cos(t)'),[-pi,pi])