Hello everyone!

I'm not experienced user since I am new to maple, right now I am struggling with partial derivatives.

I want to derivative formula L over diff(x(t), t). Im using dot notation.

Variable diff(x(t), t) is hidden under the name predkosc_x but using this variable name instead of x(t) with a dot also is not working.

What am I doing wrong that I cant derivative over few varaibles?

Also when im trying it this way

I also fail