I'm trying to solve an equation, and while it work, "plain"
Solve returns two solutions that are, in the specific case, of no interest.
Clear[r, h, V] V[r_, h_] := \[Pi] r^2 h A[r_, h_] := \[Pi] r^2 + 2 \[Pi] r h h0 = h /. Solve[V[r, h] == V0, h][] D[A[r, h0], r] Solve[D[A[r, h0], r] == 0, r]
So I tried, as suggested on some web pages,
Solve[D[A[r, h0], r] == 0 && r > 0, r]
What is the correct syntax to get the correct solution? TIA.
(N.B.: Though probably not important for the question, the mathematical problem above is about how to find the radius $r$ and height $h$ for a circular cylinder with a bottom (no top) that consumes the least material given a volume $V_0$.)