Question: Trouble calculating partial derivative in Maple

Hi all,

I have the following function (with parameters/constants a, b, and p_2A ):

I want to calculate its partial derivative with resprect to p_1A. I entered the following code to do this:

But this returns a result that was (at least, for me) unexpected:

My problem is, I don't really get what the expressions 'D(...)' mean in this equation and why they are even there. a and p_2A are supposed to be constant and thus their derivative should be zero (wtih respect to p_1A ).

I think this should be an easy problem to solve for someone more familiar with Maple, but I am new to it and have been spending the last few hours trying to figure out how to solve this problem. Any help would be highly appriciated.

Thank you in advance,

JTamas