Use the techniques from integration to find the volume of a cylinder of height h and radius r I was thinking of starting with a quadrilateral or rectangle.
starting with a horizontal line a  $y = r$, then set the area under the curve by integrating from $0$ to $h$.
$y=r$ then $y = r^2$
$$\pi \int_{0}^{h} r^2 $$
how's this?

How about 
$$\int_{0}^{h} \pi r^2 dr$$
$$= \frac{1}{3} \pi r^3$$
