Here you can find all my videos on differentiation, as well as link to a playlist containing all the videos.
Finding Stationary Points
Determining the Nature of Stationary Points (Maximums & Minimums)
Optimisation
Convavity
Points of inflection
Chain Rule for Differentiation
Proof of Chain Rule
Chain Rule Example Questions
Product Rule for Differentiation
Proof of Product Rule
Product Rule Example Questions
Quotient Rule for Differentiation
Proof of Quotient Rule
Quotient Rule Example Questions