Question: How do I automatically use differential rules like chain rule?

Let us say there is a function desribing an angle. And by deriving the math let us say the position is cos(theta). Theta is a function of time and cos is a function. How do i differentiate this and make maple see that theta is a function and not a variable.

i have tried this (x(t) is theta):

f := t -> sin(x(t));
Diff(f, t);

Did not work.What i want is the output to be.


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