time derivative of a time dependent function in maple

Question

I want to take time derivative of cos(q1) in maple such that the result will be -sin(q1)*q1_dot.

Here is what I've tried:

hh := sin(q1)*cos(q2):
f1 := (q1,q2) ->  hh:
f2 := diff(f1(q1,q2),q1):
f3 := diff(f2(t),t):

This routine does not compute d(cosq1)/dt, but leaves as it is.

Thank you in advance

Answer 1

Use the command D(cos@q1); Its result, when applied to t, will be the derivative that you are looking for.