Posted by Helga on Monday, November 21, 2011 at 1:43am.
A right circular cone has a constant volume. The height h and the base radius r can both vary. Find the rate at which h is changing with respect to r at the instant when r and h are equal.

Calculus  Steve, Monday, November 21, 2011 at 5:04am
v = pi/3 r^2 h
since v is a constant, dv = 0
0 = 2rh dr + r^2 dh
When r=h,
2r^2 dr + r^2 dh = 0
2dr + dh = 0
dh = 2dr
dh/dr = 2