Video links of the clips used:
1. What is Calculus - Lesson 4 | Integration | Don't Memorise
https://www.youtube.com/watch?v=odBiKFAdEXc
2. Volumes of Revolution (Disk Method)
https://www.youtube.com/watch?v=HHCK9iweK6U
3. Arc Length and its Applications: an Animation
https://www.youtube.com/watch?v=dO1U7NhaMLg
