Hello,

While optimizing a set of flattened equations(generated from a linear electrical circuit of 4 capacitors in series with a sinusoidal voltage source), along with 'der( )' I got '$DER' in variable list. The variable list shows it is a 'DUMMY_DER'. What is its significance? Is it possible to predict from a circuit(linear) whether its optimized form will contain '$DER' in its variable list or not?

Regards,
AC