Chain Rule Proof!.....Visually!

This video explains the Chain Rule for differentiating composite expressions showing a very simple visual 'proof' of the expression dy/dx = dy/du * du/dx as a simple system of connected gears.
I have also done a short video showing how the chain rule may be extended by adding more gears!
The link is here:
• Chain Rule... Extended!

[@davannaleah]

Pardon the wind noise. I had a personal fan here as it's quite hot!

[@davannaleah]

Minor correction. The arrow I drew on wheel U is misleading. Wheel U obviously turns in the opposite direction to wheels X and Y