MATLAB: Derivative in syms

Question

If I am using syms, and i have the following

a = b * u

then da/dt = b * du/dt.

How do I get matlab to do this rather than just assume u is not a function of t and assign a value of 1?

Answer 1

You tell MATLAB that u is a function of t.

a = subs(a,'u','u(t)');
diff(a,'t')