6.1 Finding areas
  6.1.1 Area between two curves
  6.1.2 Basic Derivation of Area Formula
 6.2 Volumes of Revolution
 6.3 Centroids (First moment of area)
  6.3.1 First moment of the area about the y axis
  6.3.2 First Moment of the area about the x axis
  6.3.3 Centroid of a plane area
  6.3.4 Meaning of the centroid
 6.4 Second Moment of Area