I looked at the geometric meaning of derivatives and the chain rule video in the 3blue1brown calculus series.
My question is that when we calculate the derivative of the product of two functions, we disregard the little rectangle in the bottom right. Please see the chain rule video at 6;20. Suppose we have a function where that quantity is so huge that we cannot disregard it.
How do we understand product rule geometrically using the methodology in that video in this case?
I guess I’m so confused that I cannot even formulate the questions properly :-)