calculating specific weight I get an answer in kg/m²s². The context panel does not allow me to change the units to N/m³. Any suggestions how to change the units to N/m³. If I use Maple I get the right units. The problem is with Maple Flow.

I am new to Maple. I am working though the manual and in chapter two I tried to get the derivative of ln(x^2+1). I am getting something completely different that the actual derivative. I tried a simple derivatie (the derivative of 2x and get 0). I do not know what I am doing wrong. Any help will be appreciated.