Uniqueness of Sinusoidal waves

Fred.

OK agreed,  as I said we are into semantics and we are talking about
two input systems.

A system that contains  a multiplier can behave in various ways
depending upon the inputs to the multiplier.

Semantically speaking, I think of the multiplier itself as non-linear
time invariant.

The system containing the multiplier is also non-liner time invariant
when the multiplier is being used as a multiplier i.e. when it  is used
to multiply two dynamic inputs to the system together.

Agreed there are subsets of uses with special cases of inputs  (static
input or an input internal to the system)  where the system that
contains the multiplier can be LTI or  where it can be LTV.

thanks

Mark