FEYN CALC SYMBOL

SelectNotFree


returns that part of expr which is not free of any occurance of x. SelectNotFree[expr, a, b, ...] is equivalent to Select[expr, !FreeQ2[#, {a, b, ...}]&], except the special cases: SelectNotFree[a, b] returns 1 and SelectNotFree[a, a] returns a (where a is not a product or a sum).