# Accepting symbolic derivatives as answers. browsing

• I'd like to ask students chain rule questions with unspecified functions, such as "evaluate the derivative of sin((h(x))^2)" and have Mobius accept a form of the answer containing, say, h'(x).

Which question type should I use?  How should the answer algorithm be coded?  I haven't been able to find any information about symbolic derivatives in the documentation.

• I think I can answer my own question.  I've managed to get this to work using the maple-graded question type, formula answer, symbolic entry only (so that prime notation can be used).  The key seems to be that the maple-generated answer contain the operator D rather than the command diff.  For example, if you ask maple to differentiate sin(f(t)), maple will respond with cos(f(t))*diff(f(t),t).  But if you ask maple to differentiate sin(f(c*t)), then it responds with cos(f(c*t))*D(f)(c*t)*c.  You just need to substitute c=1 into the result.

The following algorithm works for a question like "find the derivative of sin(f(t)), assuming f is differentiable":

$g=maple("sin(f(c*t))");$ans=maple("subs(c=1,diff(\$g,t))");

This will enable students to enter their answer symbolically using f'(t).