I believe this is intended to be a proof of the formula πrl, surface area of a cone.
A complete volume of revolution gives you a cone - the height h is the x value on a graph, the radius r is the y value. The y intercept is zero, therefore y=r/hx . All integration is with lim h→0
The Attempt at a Solution
When I tried this, I got:
=πrh! So why has this not worked? I need this to give πrl!