don't undergrad adaptive filters count? https://en.wikipedia.org/wiki/Adaptive_filter https://en.wikipedia.org/wiki/Adaptive_filter doesn't need a differentia

don't undergrad adaptive filters count? https://en.wikipedia.org/wiki/Adaptive_filter https://en.wikipedia.org/wiki/Adaptive_filter doesn't need a differentiation of the forward term, but if you squint it looks pretty close