Last time we found Lengths and Centroids.
Today we are finding Area of Surface of Revolution.
Formula for Area of Surface :
1: Revolution about x-axis ( y >= 0 )
Surface area= Int. from a to b of 2pi y((dx/dt)² + (dy/dt)²)^(1/2) dt (1)
2: Revolution about y-axis ( x >= 0 )
Surface area= Int. from a to b of 2pi x((dx/dt)² + (dy/dt)²)^(1/2) dt (2)