I have now sorted the first part of this question but cant get anywhere with part(b):
3) given area of ellipse is and that the volume generated when this area rotates through about the -axis is
use pappus' theorem to find the centroid.
for this i get the answer but not sure if its ok.
by pappus,with -coord of centroid
V=Axdistance travelled by G
so
I am unable to do the next part of the question:
b) find the first moment about Ox of that part of the area for which y>=0
i seem to need the perimeter of the ellipse here?
the answer in the book is